Ventral Tegmental Area: A region in the MESENCEPHALON which is dorsomedial to the SUBSTANTIA NIGRA and ventral to the RED NUCLEUS. The mesocortical and mesolimbic dopaminergic systems originate here, including an important projection to the NUCLEUS ACCUMBENS. Overactivity of the cells in this area has been suspected to contribute to the positive symptoms of SCHIZOPHRENIA.Tegmentum Mesencephali: Portion of midbrain situated under the dorsal TECTUM MESENCEPHALI. The two ventrolateral cylindrical masses or peduncles are large nerve fiber bundles providing a tract of passage between the FOREBRAIN with the HINDBRAIN. Ventral MIDBRAIN also contains three colorful structures: the GRAY MATTER (PERIAQUEDUCTAL GRAY), the black substance (SUBSTANTIA NIGRA), and the RED NUCLEUS.Dopamine: One of the catecholamine NEUROTRANSMITTERS in the brain. It is derived from TYROSINE and is the precursor to NOREPINEPHRINE and EPINEPHRINE. Dopamine is a major transmitter in the extrapyramidal system of the brain, and important in regulating movement. A family of receptors (RECEPTORS, DOPAMINE) mediate its action.Nucleus Accumbens: Collection of pleomorphic cells in the caudal part of the anterior horn of the LATERAL VENTRICLE, in the region of the OLFACTORY TUBERCLE, lying between the head of the CAUDATE NUCLEUS and the ANTERIOR PERFORATED SUBSTANCE. It is part of the so-called VENTRAL STRIATUM, a composite structure considered part of the BASAL GANGLIA.Dopaminergic Neurons: Neurons whose primary neurotransmitter is DOPAMINE.Cocaine: An alkaloid ester extracted from the leaves of plants including coca. It is a local anesthetic and vasoconstrictor and is clinically used for that purpose, particularly in the eye, ear, nose, and throat. It also has powerful central nervous system effects similar to the amphetamines and is a drug of abuse. Cocaine, like amphetamines, acts by multiple mechanisms on brain catecholaminergic neurons; the mechanism of its reinforcing effects is thought to involve inhibition of dopamine uptake.Mesencephalon: The middle of the three primitive cerebral vesicles of the embryonic brain. Without further subdivision, midbrain develops into a short, constricted portion connecting the PONS and the DIENCEPHALON. Midbrain contains two major parts, the dorsal TECTUM MESENCEPHALI and the ventral TEGMENTUM MESENCEPHALI, housing components of auditory, visual, and other sensorimoter systems.Reward: An object or a situation that can serve to reinforce a response, to satisfy a motive, or to afford pleasure.Substantia Nigra: The black substance in the ventral midbrain or the nucleus of cells containing the black substance. These cells produce DOPAMINE, an important neurotransmitter in regulation of the sensorimotor system and mood. The dark colored MELANIN is a by-product of dopamine synthesis.Tyrosine 3-Monooxygenase: An enzyme that catalyzes the conversion of L-tyrosine, tetrahydrobiopterin, and oxygen to 3,4-dihydroxy-L-phenylalanine, dihydrobiopterin, and water. EC 1.14.16.2.Rats, Sprague-Dawley: A strain of albino rat used widely for experimental purposes because of its calmness and ease of handling. It was developed by the Sprague-Dawley Animal Company.Neurons: The basic cellular units of nervous tissue. Each neuron consists of a body, an axon, and dendrites. Their purpose is to receive, conduct, and transmit impulses in the NERVOUS SYSTEM.Self Administration: Administration of a drug or chemical by the individual under the direction of a physician. It includes administration clinically or experimentally, by human or animal.Quinpirole: A dopamine D2/D3 receptor agonist.Microinjections: The injection of very small amounts of fluid, often with the aid of a microscope and microsyringes.Dopamine Antagonists: Drugs that bind to but do not activate DOPAMINE RECEPTORS, thereby blocking the actions of dopamine or exogenous agonists. Many drugs used in the treatment of psychotic disorders (ANTIPSYCHOTIC AGENTS) are dopamine antagonists, although their therapeutic effects may be due to long-term adjustments of the brain rather than to the acute effects of blocking dopamine receptors. Dopamine antagonists have been used for several other clinical purposes including as ANTIEMETICS, in the treatment of Tourette syndrome, and for hiccup. Dopamine receptor blockade is associated with NEUROLEPTIC MALIGNANT SYNDROME.Dopamine Uptake Inhibitors: Drugs that block the transport of DOPAMINE into axon terminals or into storage vesicles within terminals. Most of the ADRENERGIC UPTAKE INHIBITORS also inhibit dopamine uptake.Dopamine Agonists: Drugs that bind to and activate dopamine receptors.Receptors, Dopamine D2: A subfamily of G-PROTEIN-COUPLED RECEPTORS that bind the neurotransmitter DOPAMINE and modulate its effects. D2-class receptor genes contain INTRONS, and the receptors inhibit ADENYLYL CYCLASES.Conditioning, Operant: Learning situations in which the sequence responses of the subject are instrumental in producing reinforcement. When the correct response occurs, which involves the selection from among a repertoire of responses, the subject is immediately reinforced.Limbic System: A set of forebrain structures common to all mammals that is defined functionally and anatomically. It is implicated in the higher integration of visceral, olfactory, and somatic information as well as homeostatic responses including fundamental survival behaviors (feeding, mating, emotion). For most authors, it includes the AMYGDALA; EPITHALAMUS; GYRUS CINGULI; hippocampal formation (see HIPPOCAMPUS); HYPOTHALAMUS; PARAHIPPOCAMPAL GYRUS; SEPTAL NUCLEI; anterior nuclear group of thalamus, and portions of the basal ganglia. (Parent, Carpenter's Human Neuroanatomy, 9th ed, p744; NeuroNames, http://rprcsgi.rprc.washington.edu/neuronames/index.html (September 2, 1998)).Neural Pathways: Neural tracts connecting one part of the nervous system with another.Rats, Long-Evans: An outbred strain of rats developed in 1915 by crossing several Wistar Institute white females with a wild gray male. Inbred strains have been derived from this original outbred strain, including Long-Evans cinnamon rats (RATS, INBRED LEC) and Otsuka-Long-Evans-Tokushima Fatty rats (RATS, INBRED OLETF), which are models for Wilson's disease and non-insulin dependent diabetes mellitus, respectively.Ethanol: A clear, colorless liquid rapidly absorbed from the gastrointestinal tract and distributed throughout the body. It has bactericidal activity and is used often as a topical disinfectant. It is widely used as a solvent and preservative in pharmaceutical preparations as well as serving as the primary ingredient in ALCOHOLIC BEVERAGES.Central Nervous System Depressants: A very loosely defined group of drugs that tend to reduce the activity of the central nervous system. The major groups included here are ethyl alcohol, anesthetics, hypnotics and sedatives, narcotics, and tranquilizing agents (antipsychotics and antianxiety agents).Behavior, Animal: The observable response an animal makes to any situation.Self Stimulation: Stimulation of the brain, which is self-administered. The stimulation may result in negative or positive reinforcement.gamma-Aminobutyric Acid: The most common inhibitory neurotransmitter in the central nervous system.Salicylamides: Amides of salicylic acid.Motor Activity: The physical activity of a human or an animal as a behavioral phenomenon.Nicotine: Nicotine is highly toxic alkaloid. It is the prototypical agonist at nicotinic cholinergic receptors where it dramatically stimulates neurons and ultimately blocks synaptic transmission. Nicotine is also important medically because of its presence in tobacco smoke.Receptors, Dopamine D1: A subfamily of G-PROTEIN-COUPLED RECEPTORS that bind the neurotransmitter DOPAMINE and modulate its effects. D1-class receptor genes lack INTRONS, and the receptors stimulate ADENYLYL CYCLASES.Microdialysis: A technique for measuring extracellular concentrations of substances in tissues, usually in vivo, by means of a small probe equipped with a semipermeable membrane. Substances may also be introduced into the extracellular space through the membrane.Receptors, Dopamine: Cell-surface proteins that bind dopamine with high affinity and trigger intracellular changes influencing the behavior of cells.Amphetamine: A powerful central nervous system stimulant and sympathomimetic. Amphetamine has multiple mechanisms of action including blocking uptake of adrenergics and dopamine, stimulation of release of monamines, and inhibiting monoamine oxidase. Amphetamine is also a drug of abuse and a psychotomimetic. The l- and the d,l-forms are included here. The l-form has less central nervous system activity but stronger cardiovascular effects. The d-form is DEXTROAMPHETAMINE.Reinforcement (Psychology): The strengthening of a conditioned response.Morphine: The principal alkaloid in opium and the prototype opiate analgesic and narcotic. Morphine has widespread effects in the central nervous system and on smooth muscle.Vesicular Glutamate Transport Protein 2: A vesicular glutamate transporter protein that is predominately expressed in the DIENCEPHALON and lower brainstem regions of the CENTRAL NERVOUS SYSTEM.GABA Agonists: Endogenous compounds and drugs that bind to and activate GAMMA-AMINOBUTYRIC ACID receptors (RECEPTORS, GABA).Habenula: A small protuberance at the dorsal, posterior corner of the wall of the THIRD VENTRICLE, adjacent to the dorsal THALAMUS and PINEAL BODY. It contains the habenular nuclei and is a major part of the epithalamus.Glutamic Acid: A non-essential amino acid naturally occurring in the L-form. Glutamic acid is the most common excitatory neurotransmitter in the CENTRAL NERVOUS SYSTEM.Septal Nuclei: Neural nuclei situated in the septal region. They have afferent and cholinergic efferent connections with a variety of FOREBRAIN and BRAIN STEM areas including the HIPPOCAMPAL FORMATION, the LATERAL HYPOTHALAMUS, the tegmentum, and the AMYGDALA. Included are the dorsal, lateral, medial, and triangular septal nuclei, septofimbrial nucleus, nucleus of diagonal band, nucleus of anterior commissure, and the nucleus of stria terminalis.Narcotics: Agents that induce NARCOSIS. Narcotics include agents that cause somnolence or induced sleep (STUPOR); natural or synthetic derivatives of OPIUM or MORPHINE or any substance that has such effects. They are potent inducers of ANALGESIA and OPIOID-RELATED DISORDERS.Baclofen: A GAMMA-AMINOBUTYRIC ACID derivative that is a specific agonist of GABA-B RECEPTORS. It is used in the treatment of MUSCLE SPASTICITY, especially that due to SPINAL CORD INJURIES. Its therapeutic effects result from actions at spinal and supraspinal sites, generally the reduction of excitatory transmission.Stereotaxic Techniques: Techniques used mostly during brain surgery which use a system of three-dimensional coordinates to locate the site to be operated on.Heroin: A narcotic analgesic that may be habit-forming. It is a controlled substance (opium derivative) listed in the U.S. Code of Federal Regulations, Title 21 Parts 329.1, 1308.11 (1987). Sale is forbidden in the United States by Federal statute. (Merck Index, 11th ed)Benzazepines: Compounds with BENZENE fused to AZEPINES.Prefrontal Cortex: The rostral part of the frontal lobe, bounded by the inferior precentral fissure in humans, which receives projection fibers from the MEDIODORSAL NUCLEUS OF THE THALAMUS. The prefrontal cortex receives afferent fibers from numerous structures of the DIENCEPHALON; MESENCEPHALON; and LIMBIC SYSTEM as well as cortical afferents of visual, auditory, and somatic origin.Substance Withdrawal Syndrome: Physiological and psychological symptoms associated with withdrawal from the use of a drug after prolonged administration or habituation. The concept includes withdrawal from smoking or drinking, as well as withdrawal from an administered drug.2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-benzazepine: A selective D1 dopamine receptor agonist used primarily as a research tool.Inhibitory Postsynaptic Potentials: Hyperpolarization of membrane potentials at the SYNAPTIC MEMBRANES of target neurons during NEUROTRANSMISSION. They are local changes which diminish responsiveness to excitatory signals.Analysis of Variance: A statistical technique that isolates and assesses the contributions of categorical independent variables to variation in the mean of a continuous dependent variable.Receptors, Opioid, mu: A class of opioid receptors recognized by its pharmacological profile. Mu opioid receptors bind, in decreasing order of affinity, endorphins, dynorphins, met-enkephalin, and leu-enkephalin. They have also been shown to be molecular receptors for morphine.Mamillary Bodies: A pair of nuclei and associated gray matter in the interpeduncular space rostral to the posterior perforated substance in the posterior hypothalamus.Action Potentials: Abrupt changes in the membrane potential that sweep along the CELL MEMBRANE of excitable cells in response to excitation stimuli.Cocaine-Related Disorders: Disorders related or resulting from use of cocaine.Dopamine Agents: Any drugs that are used for their effects on dopamine receptors, on the life cycle of dopamine, or on the survival of dopaminergic neurons.Neurotensin: A biologically active tridecapeptide isolated from the hypothalamus. It has been shown to induce hypotension in the rat, to stimulate contraction of guinea pig ileum and rat uterus, and to cause relaxation of rat duodenum. There is also evidence that it acts as both a peripheral and a central nervous system neurotransmitter.Stilbamidines: STILBENES with AMIDINES attached.GABAergic Neurons: Neurons whose primary neurotransmitter is GAMMA-AMINOBUTYRIC ACID.Serotonin 5-HT3 Receptor Agonists: Endogenous compounds and drugs that specifically stimulate SEROTONIN 5-HT3 RECEPTORS.Muscimol: A neurotoxic isoxazole isolated from species of AMANITA. It is obtained by decarboxylation of IBOTENIC ACID. Muscimol is a potent agonist of GABA-A RECEPTORS and is used mainly as an experimental tool in animal and tissue studies.Enkephalin, Ala(2)-MePhe(4)-Gly(5)-: An enkephalin analog that selectively binds to the MU OPIOID RECEPTOR. It is used as a model for drug permeability experiments.Dose-Response Relationship, Drug: The relationship between the dose of an administered drug and the response of the organism to the drug.Neuronal Tract-Tracers: Substances used to identify the location and to characterize the types of NEURAL PATHWAYS.Synaptic Transmission: The communication from a NEURON to a target (neuron, muscle, or secretory cell) across a SYNAPSE. In chemical synaptic transmission, the presynaptic neuron releases a NEUROTRANSMITTER that diffuses across the synaptic cleft and binds to specific synaptic receptors, activating them. The activated receptors modulate specific ion channels and/or second-messenger systems in the postsynaptic cell. In electrical synaptic transmission, electrical signals are communicated as an ionic current flow across ELECTRICAL SYNAPSES.Receptors, AMPA: A class of ionotropic glutamate receptors characterized by their affinity for the agonist AMPA (alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid).Nicotinic Agonists: Drugs that bind to and activate nicotinic cholinergic receptors (RECEPTORS, NICOTINIC). Nicotinic agonists act at postganglionic nicotinic receptors, at neuroeffector junctions in the peripheral nervous system, and at nicotinic receptors in the central nervous system. Agents that function as neuromuscular depolarizing blocking agents are included here because they activate nicotinic receptors, although they are used clinically to block nicotinic transmission.Nicotinic Antagonists: Drugs that bind to nicotinic cholinergic receptors (RECEPTORS, NICOTINIC) and block the actions of acetylcholine or cholinergic agonists. Nicotinic antagonists block synaptic transmission at autonomic ganglia, the skeletal neuromuscular junction, and at central nervous system nicotinic synapses.Hypothalamic Area, Lateral: Area in the hypothalamus bounded medially by the mammillothalamic tract and the anterior column of the FORNIX (BRAIN). The medial edge of the INTERNAL CAPSULE and the subthalamic region form its lateral boundary. It contains the lateral hypothalamic nucleus, tuberomammillary nucleus, lateral tuberal nuclei, and fibers of the MEDIAL FOREBRAIN BUNDLE.Drug-Seeking Behavior: Activities performed to obtain licit or illicit substances.Mecamylamine: A nicotinic antagonist that is well absorbed from the gastrointestinal tract and crosses the blood-brain barrier. Mecamylamine has been used as a ganglionic blocker in treating hypertension, but, like most ganglionic blockers, is more often used now as a research tool.Neural Inhibition: The function of opposing or restraining the excitation of neurons or their target excitable cells.Electric Stimulation: Use of electric potential or currents to elicit biological responses.GABA-B Receptor Agonists: Endogenous compounds and drugs that bind to and activate GABA-B RECEPTORS.Dopamine Plasma Membrane Transport Proteins: Sodium chloride-dependent neurotransmitter symporters located primarily on the PLASMA MEMBRANE of dopaminergic neurons. They remove DOPAMINE from the EXTRACELLULAR SPACE by high affinity reuptake into PRESYNAPTIC TERMINALS and are the target of DOPAMINE UPTAKE INHIBITORS.Rats, Wistar: A strain of albino rat developed at the Wistar Institute that has spread widely at other institutions. This has markedly diluted the original strain.Excitatory Amino Acid Antagonists: Drugs that bind to but do not activate excitatory amino acid receptors, thereby blocking the actions of agonists.Central Nervous System Stimulants: A loosely defined group of drugs that tend to increase behavioral alertness, agitation, or excitation. They work by a variety of mechanisms, but usually not by direct excitation of neurons. The many drugs that have such actions as side effects to their main therapeutic use are not included here.Electrophysiology: The study of the generation and behavior of electrical charges in living organisms particularly the nervous system and the effects of electricity on living organisms.Conditioning (Psychology): A general term referring to the learning of some particular response.Brain: The part of CENTRAL NERVOUS SYSTEM that is contained within the skull (CRANIUM). Arising from the NEURAL TUBE, the embryonic brain is comprised of three major parts including PROSENCEPHALON (the forebrain); MESENCEPHALON (the midbrain); and RHOMBENCEPHALON (the hindbrain). The developed brain consists of CEREBRUM; CEREBELLUM; and other structures in the BRAIN STEM.Sulpiride: A dopamine D2-receptor antagonist. It has been used therapeutically as an antidepressant, antipsychotic, and as a digestive aid. (From Merck Index, 11th ed)Benzeneacetamides: Compounds based on benzeneacetamide, that are similar in structure to ACETANILIDES.Afferent Pathways: Nerve structures through which impulses are conducted from a peripheral part toward a nerve center.Drug Administration Routes: The various ways of administering a drug or other chemical to a site in a patient or animal from where the chemical is absorbed into the blood and delivered to the target tissue.EthylaminesGABA Antagonists: Drugs that bind to but do not activate GABA RECEPTORS, thereby blocking the actions of endogenous GAMMA-AMINOBUTYRIC ACID and GABA RECEPTOR AGONISTS.Proto-Oncogene Proteins c-fos: Cellular DNA-binding proteins encoded by the c-fos genes (GENES, FOS). They are involved in growth-related transcriptional control. c-fos combines with c-jun (PROTO-ONCOGENE PROTEINS C-JUN) to form a c-fos/c-jun heterodimer (TRANSCRIPTION FACTOR AP-1) that binds to the TRE (TPA-responsive element) in promoters of certain genes.Neuroanatomical Tract-Tracing Techniques: Methods used to label and follow the course of NEURAL PATHWAYS by AXONAL TRANSPORT of injected NEURONAL TRACT-TRACERS.Pons: The front part of the hindbrain (RHOMBENCEPHALON) that lies between the MEDULLA and the midbrain (MESENCEPHALON) ventral to the cerebellum. It is composed of two parts, the dorsal and the ventral. The pons serves as a relay station for neural pathways between the CEREBELLUM to the CEREBRUM.Patch-Clamp Techniques: An electrophysiologic technique for studying cells, cell membranes, and occasionally isolated organelles. All patch-clamp methods rely on a very high-resistance seal between a micropipette and a membrane; the seal is usually attained by gentle suction. The four most common variants include on-cell patch, inside-out patch, outside-out patch, and whole-cell clamp. Patch-clamp methods are commonly used to voltage clamp, that is control the voltage across the membrane and measure current flow, but current-clamp methods, in which the current is controlled and the voltage is measured, are also used.Corpus Striatum: Striped GRAY MATTER and WHITE MATTER consisting of the NEOSTRIATUM and paleostriatum (GLOBUS PALLIDUS). It is located in front of and lateral to the THALAMUS in each cerebral hemisphere. The gray substance is made up of the CAUDATE NUCLEUS and the lentiform nucleus (the latter consisting of the GLOBUS PALLIDUS and PUTAMEN). The WHITE MATTER is the INTERNAL CAPSULE.Flupenthixol: A thioxanthene neuroleptic that, unlike CHLORPROMAZINE, is claimed to have CNS-activating properties. It is used in the treatment of psychoses although not in excited or manic patients. (From Martindale, The Extra Pharmacopoeia, 30th ed, p595)Receptors, Nicotinic: One of the two major classes of cholinergic receptors. Nicotinic receptors were originally distinguished by their preference for NICOTINE over MUSCARINE. They are generally divided into muscle-type and neuronal-type (previously ganglionic) based on pharmacology, and subunit composition of the receptors.Drug Interactions: The action of a drug that may affect the activity, metabolism, or toxicity of another drug.Apomorphine: A derivative of morphine that is a dopamine D2 agonist. It is a powerful emetic and has been used for that effect in acute poisoning. It has also been used in the diagnosis and treatment of parkinsonism, but its adverse effects limit its use.Receptor, Muscarinic M5: A specific subtype of muscarinic receptor found in a variety of locations including the SALIVARY GLANDS and the SUBSTANTIA NIGRA and VENTRAL TEGMENTAL AREA of the BRAIN.Medial Forebrain Bundle: A complex group of fibers arising from the basal olfactory regions, the periamygdaloid region, and the septal nuclei, and passing to the lateral hypothalamus. Some fibers continue into the tegmentum.Receptors, N-Methyl-D-Aspartate: A class of ionotropic glutamate receptors characterized by affinity for N-methyl-D-aspartate. NMDA receptors have an allosteric binding site for glycine which must be occupied for the channel to open efficiently and a site within the channel itself to which magnesium ions bind in a voltage-dependent manner. The positive voltage dependence of channel conductance and the high permeability of the conducting channel to calcium ions (as well as to monovalent cations) are important in excitotoxicity and neuronal plasticity.Receptors, GABA-B: A subset of GABA RECEPTORS that signal through their interaction with HETEROTRIMERIC G-PROTEINS.Infusions, Intraventricular: The delivery of a drug into a fluid-filled cavity of the brain.Pedunculopontine Tegmental Nucleus: Dense collection of cells in the caudal pontomesencephalic tegmentum known to play a role in the functional organization of the BASAL GANGLIA and in the modulation of the thalamocortical neuronal system.Alcohol-Induced Disorders, Nervous System: Acute and chronic neurologic disorders associated with the various neurologic effects of ETHANOL. Primary sites of injury include the brain and peripheral nerves.Oncogene Proteins v-fos: Transforming proteins coded by fos oncogenes. These proteins have been found in the Finkel-Biskis-Jinkins (FBJ-MSV) and Finkel-Biskis-Reilly (FBR-MSV) murine sarcoma viruses which induce osteogenic sarcomas in mice. The FBJ-MSV v-fos gene encodes a p55-kDa protein and the FBR-MSV v-fos gene encodes a p75-kDa fusion protein.Exploratory Behavior: The tendency to explore or investigate a novel environment. It is considered a motivation not clearly distinguishable from curiosity.Behavior, Addictive: The observable, measurable, and often pathological activity of an organism that portrays its inability to overcome a habit resulting in an insatiable craving for a substance or for performing certain acts. The addictive behavior includes the emotional and physical overdependence on the object of habit in increasing amount or frequency.Appetitive Behavior: Animal searching behavior. The variable introductory phase of an instinctive behavior pattern or sequence, e.g., looking for food, or sequential courtship patterns prior to mating.Locus Coeruleus: Bluish-colored region in the superior angle of the FOURTH VENTRICLE floor, corresponding to melanin-like pigmented nerve cells which lie lateral to the PERIAQUEDUCTAL GRAY.Mice, Inbred C57BLKynurenic Acid: A broad-spectrum excitatory amino acid antagonist used as a research tool.Receptors, GABA-A: Cell surface proteins which bind GAMMA-AMINOBUTYRIC ACID and contain an integral membrane chloride channel. Each receptor is assembled as a pentamer from a pool of at least 19 different possible subunits. The receptors belong to a superfamily that share a common CYSTEINE loop.Amygdala: Almond-shaped group of basal nuclei anterior to the INFERIOR HORN OF THE LATERAL VENTRICLE of the TEMPORAL LOBE. The amygdala is part of the limbic system.Sexual Behavior, Animal: Sexual activities of animals.Ibogaine: One of several indole alkaloids extracted from Tabernanthe iboga, Baill. It has a complex pharmacological profile, and interacts with multiple systems of neurotransmission. Ibogaine has psychoactive properties and appears to modulate tolerance to opiates.Injections: Introduction of substances into the body using a needle and syringe.Analgesics, Opioid: Compounds with activity like OPIATE ALKALOIDS, acting at OPIOID RECEPTORS. Properties include induction of ANALGESIA or NARCOSIS.Cues: Signals for an action; that specific portion of a perceptual field or pattern of stimuli to which a subject has learned to respond.Conditioning, Classical: Learning that takes place when a conditioned stimulus is paired with an unconditioned stimulus.Gene Knock-In Techniques: Techniques used to add in exogenous gene sequence such as mutated genes; REPORTER GENES, to study mechanisms of gene expression; or regulatory control sequences, to study effects of temporal changes to GENE EXPRESSION.Synapses: Specialized junctions at which a neuron communicates with a target cell. At classical synapses, a neuron's presynaptic terminal releases a chemical transmitter stored in synaptic vesicles which diffuses across a narrow synaptic cleft and activates receptors on the postsynaptic membrane of the target cell. The target may be a dendrite, cell body, or axon of another neuron, or a specialized region of a muscle or secretory cell. Neurons may also communicate via direct electrical coupling with ELECTRICAL SYNAPSES. Several other non-synaptic chemical or electric signal transmitting processes occur via extracellular mediated interactions.Receptors, Dopamine D5: A subtype of dopamine D1 receptors that has higher affinity for DOPAMINE and differentially couples to GTP-BINDING PROTEINS.Glutamate Decarboxylase: A pyridoxal-phosphate protein that catalyzes the alpha-decarboxylation of L-glutamic acid to form gamma-aminobutyric acid and carbon dioxide. The enzyme is found in bacteria and in invertebrate and vertebrate nervous systems. It is the rate-limiting enzyme in determining GAMMA-AMINOBUTYRIC ACID levels in normal nervous tissues. The brain enzyme also acts on L-cysteate, L-cysteine sulfinate, and L-aspartate. EC 4.1.1.15.Optogenetics: The combination of genetic and optical methods in controlling specific events with temporal precision in targeted cells of a functioning intact biological system.Pregnanolone: A pregnane found in the urine of pregnant women and sows. It has anesthetic, hypnotic, and sedative properties.Extinction, Psychological: The procedure of presenting the conditioned stimulus without REINFORCEMENT to an organism previously conditioned. It refers also to the diminution of a conditioned response resulting from this procedure.Excitatory Postsynaptic Potentials: Depolarization of membrane potentials at the SYNAPTIC MEMBRANES of target neurons during neurotransmission. Excitatory postsynaptic potentials can singly or in summation reach the trigger threshold for ACTION POTENTIALS.Motivation: Those factors which cause an organism to behave or act in either a goal-seeking or satisfying manner. They may be influenced by physiological drives or by external stimuli.Neuropeptides: Peptides released by NEURONS as intercellular messengers. Many neuropeptides are also hormones released by non-neuronal cells.Time Factors: Elements of limited time intervals, contributing to particular results or situations.Orexin Receptors: G-protein-coupled NEUROPEPTIDE RECEPTORS that have specificity for OREXINS and play a role in appetite control, and sleep-wake cycles. Two principle receptor types exist, each having a specificity for OREXIN A and OREXIN B peptide subtypes.Hypothalamus, Posterior: The part of the hypothalamus posterior to the middle region consisting of several nuclei including the medial maxillary nucleus, lateral mammillary nucleus, and posterior hypothalamic nucleus (posterior hypothalamic area). The posterior hypothalamic area is concerned with control of sympathetic responses and is sensitive to conditions of decreasing temperature and controls the mechanisms for the conservation and increased production of heat.Dihydro-beta-Erythroidine: Dihydro analog of beta-erythroidine, which is isolated from the seeds and other plant parts of Erythrina sp. Leguminosae. It is an alkaloid with curarimimetic properties.Neuronal Plasticity: The capacity of the NERVOUS SYSTEM to change its reactivity as the result of successive activations.Rats, Inbred F344Immunohistochemistry: Histochemical localization of immunoreactive substances using labeled antibodies as reagents.2-Amino-5-phosphonovalerate: The D-enantiomer is a potent and specific antagonist of NMDA glutamate receptors (RECEPTORS, N-METHYL-D-ASPARTATE). The L form is inactive at NMDA receptors but may affect the AP4 (2-amino-4-phosphonobutyrate; APB) excitatory amino acid receptors.Autoradiography: The making of a radiograph of an object or tissue by recording on a photographic plate the radiation emitted by radioactive material within the object. (Dorland, 27th ed)Locomotion: Movement or the ability to move from one place or another. It can refer to humans, vertebrate or invertebrate animals, and microorganisms.Haloperidol: A phenyl-piperidinyl-butyrophenone that is used primarily to treat SCHIZOPHRENIA and other PSYCHOSES. It is also used in schizoaffective disorder, DELUSIONAL DISORDERS, ballism, and TOURETTE SYNDROME (a drug of choice) and occasionally as adjunctive therapy in INTELLECTUAL DISABILITY and the chorea of HUNTINGTON DISEASE. It is a potent antiemetic and is used in the treatment of intractable HICCUPS. (From AMA Drug Evaluations Annual, 1994, p279)Spatial Behavior: Reactions of an individual or groups of individuals with relation to the immediate surrounding area including the animate or inanimate objects within that area.Serotonin 5-HT2 Receptor Antagonists: Drugs that bind to but do not activate SEROTONIN 5-HT2 RECEPTORS, thereby blocking the actions of SEROTONIN or SEROTONIN 5-HT2 RECEPTOR AGONISTS. Included under this heading are antagonists for one or more specific 5-HT2 receptor subtypes.QuinoxalinesNarcotic Antagonists: Agents inhibiting the effect of narcotics on the central nervous system.Receptor, Serotonin, 5-HT2C: A serotonin receptor subtype found primarily in the CENTRAL NERVOUS SYSTEM and the CHOROID PLEXUS. This receptor subtype is believed to mediate the anorectic action of SEROTONIN, while selective antagonists of the 5-HT2C receptor appear to induce ANXIETY. Several isoforms of this receptor subtype exist, due to adenine deaminase editing of the receptor mRNA.Raclopride: A substituted benzamide that has antipsychotic properties. It is a dopamine D2 receptor (see RECEPTORS, DOPAMINE D2) antagonist.Ibotenic Acid: A neurotoxic isoxazole (similar to KAINIC ACID and MUSCIMOL) found in AMANITA mushrooms. It causes motor depression, ataxia, and changes in mood, perceptions and feelings, and is a potent excitatory amino acid agonist.Iontophoresis: Therapeutic introduction of ions of soluble salts into tissues by means of electric current. In medical literature it is commonly used to indicate the process of increasing the penetration of drugs into surface tissues by the application of electric current. It has nothing to do with ION EXCHANGE; AIR IONIZATION nor PHONOPHORESIS, none of which requires current.GABA Agents: Substances used for their pharmacological actions on GABAergic systems. GABAergic agents include agonists, antagonists, degradation or uptake inhibitors, depleters, precursors, and modulators of receptor function.3,4-Dihydroxyphenylacetic Acid: A deaminated metabolite of LEVODOPA.Presynaptic Terminals: The distal terminations of axons which are specialized for the release of neurotransmitters. Also included are varicosities along the course of axons which have similar specializations and also release transmitters. Presynaptic terminals in both the central and peripheral nervous systems are included.Photomicrography: Photography of objects viewed under a microscope using ordinary photographic methods.Extracellular Space: Interstitial space between cells, occupied by INTERSTITIAL FLUID as well as amorphous and fibrous substances. For organisms with a CELL WALL, the extracellular space includes everything outside of the CELL MEMBRANE including the PERIPLASM and the cell wall.Methamphetamine: A central nervous system stimulant and sympathomimetic with actions and uses similar to DEXTROAMPHETAMINE. The smokable form is a drug of abuse and is referred to as crank, crystal, crystal meth, ice, and speed.Vesicular Glutamate Transport Protein 1: A vesicular glutamate transporter protein that is predominately expressed in TELENCEPHALON of the BRAIN.Morphine Dependence: Strong dependence, both physiological and emotional, upon morphine.Love: Affection; in psychiatry commonly refers to pleasure, particularly as it applies to gratifying experiences between individuals.Lateral Thalamic Nuclei: A narrow strip of cell groups on the dorsomedial surface of the thalamus. It includes the lateral dorsal nucleus, lateral posterior nucleus, and the PULVINAR.Receptors, Serotonin, 5-HT2: A subclass of G-protein coupled SEROTONIN receptors that couple preferentially to the GQ-G11 G-PROTEINS resulting in increased intracellular levels of INOSITOL PHOSPHATES and free CALCIUM.Dendrites: Extensions of the nerve cell body. They are short and branched and receive stimuli from other NEURONS.BenzoxazolesExcitatory Amino Acid Agonists: Drugs that bind to and activate excitatory amino acid receptors.Basal Ganglia: Large subcortical nuclear masses derived from the telencephalon and located in the basal regions of the cerebral hemispheres.Serotonin Antagonists: Drugs that bind to but do not activate serotonin receptors, thereby blocking the actions of serotonin or SEROTONIN RECEPTOR AGONISTS.Cell Count: The number of CELLS of a specific kind, usually measured per unit volume or area of sample.Sucrose: A nonreducing disaccharide composed of GLUCOSE and FRUCTOSE linked via their anomeric carbons. It is obtained commercially from SUGARCANE, sugar beet (BETA VULGARIS), and other plants and used extensively as a food and a sweetener.Avoidance Learning: A response to a cue that is instrumental in avoiding a noxious experience.Preoptic Area: Region of hypothalamus between the ANTERIOR COMMISSURE and OPTIC CHIASM.Naloxone: A specific opiate antagonist that has no agonist activity. It is a competitive antagonist at mu, delta, and kappa opioid receptors.Oxidopamine: A neurotransmitter analogue that depletes noradrenergic stores in nerve endings and induces a reduction of dopamine levels in the brain. Its mechanism of action is related to the production of cytolytic free-radicals.Enkephalins: One of the three major families of endogenous opioid peptides. The enkephalins are pentapeptides that are widespread in the central and peripheral nervous systems and in the adrenal medulla.Feeding Behavior: Behavioral responses or sequences associated with eating including modes of feeding, rhythmic patterns of eating, and time intervals.Aminopyridines: Pyridines substituted in any position with an amino group. May be hydrogenated, but must retain at least one double bond.Heroin Dependence: Strong dependence, both physiological and emotional, upon heroin.Globus Pallidus: The representation of the phylogenetically oldest part of the corpus striatum called the paleostriatum. It forms the smaller, more medial part of the lentiform nucleus.Long-Term Potentiation: A persistent increase in synaptic efficacy, usually induced by appropriate activation of the same synapses. The phenomenological properties of long-term potentiation suggest that it may be a cellular mechanism of learning and memory.Bicuculline: An isoquinoline alkaloid obtained from Dicentra cucullaria and other plants. It is a competitive antagonist for GABA-A receptors.Efferent Pathways: Nerve structures through which impulses are conducted from a nerve center toward a peripheral site. Such impulses are conducted via efferent neurons (NEURONS, EFFERENT), such as MOTOR NEURONS, autonomic neurons, and hypophyseal neurons.Indoles: Benzopyrroles with the nitrogen at the number one carbon adjacent to the benzyl portion, in contrast to ISOINDOLES which have the nitrogen away from the six-membered ring.Domperidone: A specific blocker of dopamine receptors. It speeds gastrointestinal peristalsis, causes prolactin release, and is used as antiemetic and tool in the study of dopaminergic mechanisms.Hyperkinesis: Excessive movement of muscles of the body as a whole, which may be associated with organic or psychological disorders.Electroshock: Induction of a stress reaction in experimental subjects by means of an electrical shock; applies to either convulsive or non-convulsive states.Stereotyped Behavior: Relatively invariant mode of behavior elicited or determined by a particular situation; may be verbal, postural, or expressive.Receptors, Neuropeptide: Cell surface receptors that bind specific neuropeptides with high affinity and trigger intracellular changes influencing the behavior of cells. Many neuropeptides are also hormones outside of the nervous system.Calbindins: Calcium-binding proteins that are found in DISTAL KIDNEY TUBULES, INTESTINES, BRAIN, and other tissues where they bind, buffer and transport cytoplasmic calcium. Calbindins possess a variable number of EF-HAND MOTIFS which contain calcium-binding sites. Some isoforms are regulated by VITAMIN D.Aconitine: A C19 norditerpenoid alkaloid (DITERPENES) from the root of ACONITUM plants. It activates VOLTAGE-GATED SODIUM CHANNELS. It has been used to induce ARRHYTHMIAS in experimental animals and it has antiinflammatory and antineuralgic properties.Mediodorsal Thalamic Nucleus: The largest of the medial nuclei of the thalamus. It makes extensive connections with most of the other thalamic nuclei.Receptor, Serotonin, 5-HT1B: A serotonin receptor subtype found at high levels in the BASAL GANGLIA and the frontal cortex. It plays a role as a terminal autoreceptor that regulates the rate of SEROTONIN release from nerve endings. This serotonin receptor subtype is closely related to and has similar drug binding properties as the 5-HT1D RECEPTOR. It is particularly sensitive to the agonist SUMATRIPTAN and may be involved in mediating the drug's antimigraine effect.Receptors, Opioid, kappa: A class of opioid receptors recognized by its pharmacological profile. Kappa opioid receptors bind dynorphins with a higher affinity than endorphins which are themselves preferred to enkephalins.Alcohol Drinking: Behaviors associated with the ingesting of alcoholic beverages, including social drinking.N-Methylaspartate: An amino acid that, as the D-isomer, is the defining agonist for the NMDA receptor subtype of glutamate receptors (RECEPTORS, NMDA).Animals, Newborn: Refers to animals in the period of time just after birth.Dizocilpine Maleate: A potent noncompetitive antagonist of the NMDA receptor (RECEPTORS, N-METHYL-D-ASPARTATE) used mainly as a research tool. The drug has been considered for the wide variety of neurodegenerative conditions or disorders in which NMDA receptors may play an important role. Its use has been primarily limited to animal and tissue experiments because of its psychotropic effects.Brain Mapping: Imaging techniques used to colocalize sites of brain functions or physiological activity with brain structures.Picrotoxin: A noncompetitive antagonist at GABA-A receptors and thus a convulsant. Picrotoxin blocks the GAMMA-AMINOBUTYRIC ACID-activated chloride ionophore. Although it is most often used as a research tool, it has been used as a CNS stimulant and an antidote in poisoning by CNS depressants, especially the barbiturates.Receptors, Dopamine D3: A subtype of dopamine D2 receptors that are highly expressed in the LIMBIC SYSTEM of the brain.Brain Stem: The part of the brain that connects the CEREBRAL HEMISPHERES with the SPINAL CORD. It consists of the MESENCEPHALON; PONS; and MEDULLA OBLONGATA.Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels: A subgroup of cyclic nucleotide-regulated ION CHANNELS of the superfamily of pore-loop cation channels that are opened by hyperpolarization rather than depolarization. The ion conducting pore passes SODIUM, CALCIUM, and POTASSIUM cations with a preference for potassium.Receptors, Neurokinin-3: A class of cell surface receptors for tachykinins that prefers neurokinin B (neurokinin beta, neuromedin K) over other tachykinins. Neurokinin-3 (NK-3) receptors have been cloned and are members of the G-protein coupled receptor superfamily. They have been found in the central nervous system and in peripheral tissues.PyrrolidinesErgolines: A series of structurally-related alkaloids that contain the ergoline backbone structure.