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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.Adrenergic Neurons: Neurons whose primary neurotransmitter is EPINEPHRINE.Dopamine beta-HydroxylaseTyrosine 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.Norepinephrine: Precursor of epinephrine that is secreted by the adrenal medulla and is a widespread central and autonomic neurotransmitter. Norepinephrine is the principal transmitter of most postganglionic sympathetic fibers and of the diffuse projection system in the brain arising from the locus ceruleus. It is also found in plants and is used pharmacologically as a sympathomimetic.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.Genetic Loci: Specific regions that are mapped within a GENOME. Genetic loci are usually identified with a shorthand notation that indicates the chromosome number and the position of a specific band along the P or Q arm of the chromosome where they are found. For example the locus 6p21 is found within band 21 of the P-arm of CHROMOSOME 6. Many well known genetic loci are also known by common names that are associated with a genetic function or HEREDITARY DISEASE.Receptors, Adrenergic, alpha-2: A subclass of alpha-adrenergic receptors found on both presynaptic and postsynaptic membranes where they signal through Gi-Go G-PROTEINS. While postsynaptic alpha-2 receptors play a traditional role in mediating the effects of ADRENERGIC AGONISTS, the subset of alpha-2 receptors found on presynaptic membranes signal the feedback inhibition of NEUROTRANSMITTER release.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.Norepinephrine Plasma Membrane Transport Proteins: Sodium chloride-dependent neurotransmitter symporters located primarily on the PLASMA MEMBRANE of noradrenergic neurons. They remove NOREPINEPHRINE from the EXTRACELLULAR SPACE by high affinity reuptake into PRESYNAPTIC TERMINALS. It regulates signal amplitude and duration at noradrenergic synapses and is the target of ADRENERGIC UPTAKE INHIBITORS.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.Raphe Nuclei: Collections of small neurons centrally scattered among many fibers from the level of the TROCHLEAR NUCLEUS in the midbrain to the hypoglossal area in the MEDULLA OBLONGATA.Galanin: A neuropeptide of 29-30 amino acids depending on the species. Galanin is widely distributed throughout the BRAIN; SPINAL CORD; and INTESTINES. There are various subtypes of GALANIN RECEPTORS implicating roles of galanin in regulating FOOD INTAKE; pain perception; memory; and other neuroendocrine functions.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.Corticotropin-Releasing Hormone: A peptide of about 41 amino acids that stimulates the release of ADRENOCORTICOTROPIC HORMONE. CRH is synthesized by neurons in the PARAVENTRICULAR NUCLEUS of the HYPOTHALAMUS. After being released into the pituitary portal circulation, CRH stimulates the release of ACTH from the PITUITARY GLAND. CRH can also be synthesized in other tissues, such as PLACENTA; ADRENAL MEDULLA; and TESTIS.Adrenergic alpha-2 Receptor Antagonists: Drugs that bind to and block the activation of ADRENERGIC ALPHA-2 RECEPTORS.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.Receptor, Galanin, Type 3: A galanin receptor subtype with high affinity for GALANIN-LIKE PEPTIDE and low affinity for full length GALANIN and galanin peptide fragments.Quantitative Trait Loci: Genetic loci associated with a QUANTITATIVE TRAIT.Clonidine: An imidazoline sympatholytic agent that stimulates ALPHA-2 ADRENERGIC RECEPTORS and central IMIDAZOLINE RECEPTORS. It is commonly used in the management of HYPERTENSION.Piperoxan: A benzodioxane alpha-adrenergic blocking agent with considerable stimulatory action. It has been used to diagnose PHEOCHROMOCYTOMA and as an antihypertensive agent.Adrenergic alpha-Agonists: Drugs that selectively bind to and activate alpha adrenergic receptors.Medetomidine: An agonist of RECEPTORS, ADRENERGIC ALPHA-2 that is used in veterinary medicine for its analgesic and sedative properties. It is the racemate of DEXMEDETOMIDINE.Imidazoline Receptors: Receptors of CLONIDINE and other IMIDAZOLINES. Activity of the ligands was earlier attributed to ADRENERGIC ALPHA-2 RECEPTORS. Endogenous ligands include AGMATINE, imidazoleacetic acid ribotide, and harman.Receptor, Galanin, Type 1: The most abundant galanin receptor subtype. It displays a high affinity for the full-length form of GALANIN.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.Receptor, Galanin, Type 2: A galanin receptor subtype with broad specificity for full length GALANIN, galanin peptide fragments and GALANIN-LIKE PEPTIDE.Naloxone: A specific opiate antagonist that has no agonist activity. It is a competitive antagonist at mu, delta, and kappa opioid receptors.Opioid Peptides: The endogenous peptides with opiate-like activity. The three major classes currently recognized are the ENKEPHALINS, the DYNORPHINS, and the ENDORPHINS. Each of these families derives from different precursors, proenkephalin, prodynorphin, and PRO-OPIOMELANOCORTIN, respectively. There are also at least three classes of OPIOID RECEPTORS, but the peptide families do not map to the receptors in a simple way.Droxidopa: A precursor of noradrenaline that is used in the treatment of parkinsonism. The racemic form (DL-threo-3,4-dihydroxyphenylserine) has also been used, and has been investigated in the treatment of orthostatic hypotension. There is a deficit of noradrenaline as well as of dopamine in Parkinson's disease and it has been proposed that this underlies the sudden transient freezing seen usually in advanced disease. Administration of DL-threo-3,4-dihydroxyphenylserine has been claimed to result in an improvement in this phenomenon but controlled studies have failed to demonstrate improvement. (Reynolds JEF(Ed): Martindale: The Extra Pharmacopoeia (electronic version). Micromedex, Inc, Englewood, CO, 1995)Microinjections: The injection of very small amounts of fluid, often with the aid of a microscope and microsyringes.Receptors, Catecholamine: Cell surface proteins that bind catecholamines with high affinity and trigger intracellular changes which influence the behavior of cells. The catecholamine messengers epinephrine, norepinephrine, and dopamine are synthesized from tyrosine by a common biosynthetic pathway.Yohimbine: A plant alkaloid with alpha-2-adrenergic blocking activity. Yohimbine has been used as a mydriatic and in the treatment of ERECTILE DYSFUNCTION.Morphine Dependence: Strong dependence, both physiological and emotional, upon morphine.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.Adrenergic alpha-Antagonists: Drugs that bind to but do not activate alpha-adrenergic receptors thereby blocking the actions of endogenous or exogenous adrenergic agonists. Adrenergic alpha-antagonists are used in the treatment of hypertension, vasospasm, peripheral vascular disease, shock, and pheochromocytoma.Behavior, Animal: The observable response an animal makes to any situation.Benzylamines: Toluenes in which one hydrogen of the methyl group is substituted by an amino group. Permitted are any substituents on the benzene ring or the amino group.Idazoxan: A benzodioxane-linked imidazole that has alpha-2 adrenoceptor antagonist activity.Arousal: Cortical vigilance or readiness of tone, presumed to be in response to sensory stimulation via the reticular activating system.Enkephalin, Methionine: One of the endogenous pentapeptides with morphine-like activity. It differs from LEU-ENKEPHALIN by the amino acid METHIONINE in position 5. Its first four amino acid sequence is identical to the tetrapeptide sequence at the N-terminal of BETA-ENDORPHIN.Chromosome Mapping: Any method used for determining the location of and relative distances between genes on a chromosome.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.Neuropeptides: Peptides released by NEURONS as intercellular messengers. Many neuropeptides are also hormones released by non-neuronal cells.Neural Pathways: Neural tracts connecting one part of the nervous system with another.Biogenic Monoamines: Biogenic amines having only one amine moiety. Included in this group are all natural monoamines formed by the enzymatic decarboxylation of natural amino acids.Adrenergic Uptake Inhibitors: Drugs that block the transport of adrenergic transmitters into axon terminals or into storage vesicles within terminals. The tricyclic antidepressants (ANTIDEPRESSIVE AGENTS, TRICYCLIC) and amphetamines are among the therapeutically important drugs that may act via inhibition of adrenergic transport. Many of these drugs also block transport of serotonin.