Olfactory Bulb: Ovoid body resting on the CRIBRIFORM PLATE of the ethmoid bone where the OLFACTORY NERVE terminates. The olfactory bulb contains several types of nerve cells including the mitral cells, on whose DENDRITES the olfactory nerve synapses, forming the olfactory glomeruli. The accessory olfactory bulb, which receives the projection from the VOMERONASAL ORGAN via the vomeronasal nerve, is also included here.Olfactory Nerve: The 1st cranial nerve. The olfactory nerve conveys the sense of smell. It is formed by the axons of OLFACTORY RECEPTOR NEURONS which project from the olfactory epithelium (in the nasal epithelium) to the OLFACTORY BULB.Olfactory Receptor Neurons: Neurons in the OLFACTORY EPITHELIUM with proteins (RECEPTORS, ODORANT) that bind, and thus detect, odorants. These neurons send their DENDRITES to the surface of the epithelium with the odorant receptors residing in the apical non-motile cilia. Their unmyelinated AXONS synapse in the OLFACTORY BULB of the BRAIN.Smell: The ability to detect scents or odors, such as the function of OLFACTORY RECEPTOR NEURONS.Odors: The volatile portions of substances perceptible by the sense of smell. (Grant & Hackh's Chemical Dictionary, 5th ed)Olfactory Pathways: Set of nerve fibers conducting impulses from olfactory receptors to the cerebral cortex. It includes the OLFACTORY NERVE; OLFACTORY BULB; OLFACTORY TRACT; OLFACTORY TUBERCLE; ANTERIOR PERFORATED SUBSTANCE; and OLFACTORY CORTEX.Olfactory Marker Protein: A ubiquitous, cytoplasmic protein found in mature OLFACTORY RECEPTOR NEURONS of all VERTEBRATES. It is a modulator of the olfactory SIGNAL TRANSDUCTION PATHWAY.Receptors, Odorant: Proteins, usually projecting from the cilia of olfactory receptor neurons, that specifically bind odorant molecules and trigger responses in the neurons. The large number of different odorant receptors appears to arise from several gene families or subfamilies rather than from DNA rearrangement.Olfaction Disorders: Loss of or impaired ability to smell. This may be caused by OLFACTORY NERVE DISEASES; PARANASAL SINUS DISEASES; viral RESPIRATORY TRACT INFECTIONS; CRANIOCEREBRAL TRAUMA; SMOKING; and other conditions.Olfactory Nerve Injuries: Traumatic injuries to the OLFACTORY NERVE. It may result in various olfactory dysfunction including a complete loss of smell.Olfactory Mucosa: That portion of the nasal mucosa containing the sensory nerve endings for SMELL, located at the dome of each NASAL CAVITY. The yellow-brownish olfactory epithelium consists of OLFACTORY RECEPTOR NEURONS; brush cells; STEM CELLS; and the associated olfactory glands.Vomeronasal Organ: An accessory chemoreceptor organ that is separated from the main OLFACTORY MUCOSA. It is situated at the base of nasal septum close to the VOMER and NASAL BONES. It forwards chemical signals (such as PHEROMONES) to the CENTRAL NERVOUS SYSTEM, thus influencing reproductive and social behavior. In humans, most of its structures except the vomeronasal duct undergo regression after birth.Olfactory Perception: The process by which the nature and meaning of olfactory stimuli, such as odors, are recognized and interpreted by the brain.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.Lateral Ventricles: Cavity in each of the CEREBRAL HEMISPHERES derived from the cavity of the embryonic NEURAL TUBE. They are separated from each other by the SEPTUM PELLUCIDUM, and each communicates with the THIRD VENTRICLE by the foramen of Monro, through which also the choroid plexuses (CHOROID PLEXUS) of the lateral ventricles become continuous with that of the third ventricle.Interneurons: Most generally any NEURONS which are not motor or sensory. Interneurons may also refer to neurons whose AXONS remain within a particular brain region in contrast to projection neurons, which have axons projecting to other brain regions.Neurogenesis: Formation of NEURONS which involves the differentiation and division of STEM CELLS in which one or both of the daughter cells become neurons.Dendrites: Extensions of the nerve cell body. They are short and branched and receive stimuli from other NEURONS.Sensory Receptor Cells: Specialized afferent neurons capable of transducing sensory stimuli into NERVE IMPULSES to be transmitted to the CENTRAL NERVOUS SYSTEM. Sometimes sensory receptors for external stimuli are called exteroceptors; for internal stimuli are called interoceptors and proprioceptors.Animals, Newborn: Refers to animals in the period of time just after birth.Telencephalon: The anterior subdivision of the embryonic PROSENCEPHALON or the corresponding part of the adult prosencephalon that includes the cerebrum and associated structures.Nasal Cavity: The proximal portion of the respiratory passages on either side of the NASAL SEPTUM. Nasal cavities, extending from the nares to the NASOPHARYNX, are lined with ciliated NASAL MUCOSA.Axons: Nerve fibers that are capable of rapidly conducting impulses away from the neuron cell body.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.Mice, Inbred C57BLPheromones: Chemical substances, excreted by an organism into the environment, that elicit behavioral or physiological responses from other organisms of the same species. Perception of these chemical signals may be olfactory or by contact.Pentanols: Isomeric forms and derivatives of pentanol (C5H11OH).Neuropil: A dense intricate feltwork of interwoven fine glial processes, fibrils, synaptic terminals, axons, and dendrites interspersed among the nerve cells in the gray matter of the central nervous system.Prosencephalon: The anterior of the three primitive cerebral vesicles of the embryonic brain arising from the NEURAL TUBE. It subdivides to form DIENCEPHALON and TELENCEPHALON. (Stedmans Medical Dictionary, 27th ed)Nerve Tissue ProteinsAction Potentials: Abrupt changes in the membrane potential that sweep along the CELL MEMBRANE of excitable cells in response to excitation stimuli.Zinc Sulfate: A compound given in the treatment of conditions associated with zinc deficiency such as acrodermatitis enteropathica. Externally, zinc sulfate is used as an astringent in lotions and eye drops. (Reynolds JEF(Ed): Martindale: The Extra Pharmacopoeia (electronic version). Micromedex, Inc, Englewood, CO, 1995)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.Immunohistochemistry: Histochemical localization of immunoreactive substances using labeled antibodies as reagents.Neural Inhibition: The function of opposing or restraining the excitation of neurons or their target excitable cells.Nasal Septum: The partition separating the two NASAL CAVITIES in the midplane. It is formed by the SEPTAL NASAL CARTILAGE, parts of skull bones (ETHMOID BONE; VOMER), and membranous parts.Mice, Transgenic: Laboratory mice that have been produced from a genetically manipulated EGG or EMBRYO, MAMMALIAN.Behavior, Animal: The observable response an animal makes to any situation.Neurons, Afferent: Neurons which conduct NERVE IMPULSES to the CENTRAL NERVOUS SYSTEM.Bromodeoxyuridine: A nucleoside that substitutes for thymidine in DNA and thus acts as an antimetabolite. It causes breaks in chromosomes and has been proposed as an antiviral and antineoplastic agent. It has been given orphan drug status for use in the treatment of primary brain tumors.Esthesioneuroblastoma, Olfactory: A malignant olfactory neuroblastoma arising from the olfactory epithelium of the superior nasal cavity and cribriform plate. It is uncommon (3% of nasal tumors) and rarely is associated with the production of excess hormones (e.g., SIADH, Cushing Syndrome). It has a high propensity for multiple local recurrences and bony metastases. (From Holland et al., Cancer Medicine, 3rd ed, p1245; J Laryngol Otol 1998 Jul;112(7):628-33)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.Kallmann Syndrome: A genetically heterogeneous disorder caused by hypothalamic GNRH deficiency and OLFACTORY NERVE defects. It is characterized by congenital HYPOGONADOTROPIC HYPOGONADISM and ANOSMIA, possibly with additional midline defects. It can be transmitted as an X-linked (GENETIC DISEASES, X-LINKED), an autosomal dominant, or an autosomal recessive trait.Stimulation, Chemical: The increase in a measurable parameter of a PHYSIOLOGICAL PROCESS, including cellular, microbial, and plant; immunological, cardiovascular, respiratory, reproductive, urinary, digestive, neural, musculoskeletal, ocular, and skin physiological processes; or METABOLIC PROCESS, including enzymatic and other pharmacological processes, by a drug or other chemical.Discrimination (Psychology): Differential response to different stimuli.Arthropod Antennae: Paired sense organs connected to the anterior segments of ARTHROPODS that help them navigate through the environment.Neural Stem Cells: Self-renewing cells that generate the main phenotypes of the nervous system in both the embryo and adult. Neural stem cells are precursors to both NEURONS and NEUROGLIA.Stem Cells: Relatively undifferentiated cells that retain the ability to divide and proliferate throughout postnatal life to provide progenitor cells that can differentiate into specialized cells.Habituation, Psychophysiologic: The disappearance of responsiveness to a repeated stimulation. It does not include drug habituation.Cerebral Ventricles: Four CSF-filled (see CEREBROSPINAL FLUID) cavities within the cerebral hemispheres (LATERAL VENTRICLES), in the midline (THIRD VENTRICLE) and within the PONS and MEDULLA OBLONGATA (FOURTH VENTRICLE).In Situ Hybridization: A technique that localizes specific nucleic acid sequences within intact chromosomes, eukaryotic cells, or bacterial cells through the use of specific nucleic acid-labeled probes.Evoked Potentials: Electrical responses recorded from nerve, muscle, SENSORY RECEPTOR, or area of the CENTRAL NERVOUS SYSTEM following stimulation. They range from less than a microvolt to several microvolts. The evoked potential can be auditory (EVOKED POTENTIALS, AUDITORY), somatosensory (EVOKED POTENTIALS, SOMATOSENSORY), visual (EVOKED POTENTIALS, VISUAL), or motor (EVOKED POTENTIALS, MOTOR), or other modalities that have been reported.Nerve Net: A meshlike structure composed of interconnecting nerve cells that are separated at the synaptic junction or joined to one another by cytoplasmic processes. In invertebrates, for example, the nerve net allows nerve impulses to spread over a wide area of the net because synapses can pass information in any direction.Electric Stimulation: Use of electric potential or currents to elicit biological responses.Sensory Deprivation: The absence or restriction of the usual external sensory stimuli to which the individual responds.gamma-Aminobutyric Acid: The most common inhibitory neurotransmitter in the central nervous system.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.Discrimination Learning: Learning that is manifested in the ability to respond differentially to various stimuli.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.Calbindin 2: A calbindin protein that is differentially expressed in distinct populations of NEURONS throughout the vertebrate and invertebrate NERVOUS SYSTEM, and modulates intrinsic neuronal excitability and influences LONG-TERM POTENTIATION. It is also found in LUNG, TESTIS, OVARY, KIDNEY, and BREAST, and is expressed in many tumor types found in these tissues. It is often used as an immunohistochemical marker for MESOTHELIOMA.Nasal Mucosa: The mucous lining of the NASAL CAVITY, including lining of the nostril (vestibule) and the OLFACTORY MUCOSA. Nasal mucosa consists of ciliated cells, GOBLET CELLS, brush cells, small granule cells, basal cells (STEM CELLS) and glands containing both mucous and serous cells.Sensory Thresholds: The minimum amount of stimulus energy necessary to elicit a sensory response.Kv1.3 Potassium Channel: A delayed rectifier subtype of shaker potassium channels that is the predominant VOLTAGE-GATED POTASSIUM CHANNEL of T-LYMPHOCYTES.Neuroglia: The non-neuronal cells of the nervous system. They not only provide physical support, but also respond to injury, regulate the ionic and chemical composition of the extracellular milieu, participate in the BLOOD-BRAIN BARRIER and BLOOD-RETINAL BARRIER, form the myelin insulation of nervous pathways, guide neuronal migration during development, and exchange metabolites with neurons. Neuroglia have high-affinity transmitter uptake systems, voltage-dependent and transmitter-gated ion channels, and can release transmitters, but their role in signaling (as in many other functions) is unclear.Excitatory Amino Acid Antagonists: Drugs that bind to but do not activate excitatory amino acid receptors, thereby blocking the actions of agonists.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 184.108.40.206.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.Green Fluorescent Proteins: Protein analogs and derivatives of the Aequorea victoria green fluorescent protein that emit light (FLUORESCENCE) when excited with ULTRAVIOLET RAYS. They are used in REPORTER GENES in doing GENETIC TECHNIQUES. Numerous mutants have been made to emit other colors or be sensitive to pH.Monoterpenes: Compounds with a core of 10 carbons generally formed via the mevalonate pathway from the combination of 3,3-dimethylallyl pyrophosphate and isopentenyl pyrophosphate. They are cyclized and oxidized in a variety of ways. Due to the low molecular weight many of them exist in the form of essential oils (OILS, VOLATILE).Models, Neurological: Theoretical representations that simulate the behavior or activity of the neurological system, processes or phenomena; includes the use of mathematical equations, computers, and other electronic equipment.Central Nervous System: The main information-processing organs of the nervous system, consisting of the brain, spinal cord, and meninges.Cell Movement: The movement of cells from one location to another. Distinguish from CYTOKINESIS which is the process of dividing the CYTOPLASM of a cell.Time Factors: Elements of limited time intervals, contributing to particular results or situations.Ictaluridae: A family of North American freshwater CATFISHES. It consists of four genera (Ameiurus, Ictalurus, Noturus, Pylodictis,) comprising several species, two of which are eyeless.Gene Expression Regulation, Developmental: Any of the processes by which nuclear, cytoplasmic, or intercellular factors influence the differential control of gene action during the developmental stages of an organism.Sense Organs: Specialized organs adapted for the reception of stimuli by the NERVOUS SYSTEM.Mice, Knockout: Strains of mice in which certain GENES of their GENOMES have been disrupted, or "knocked-out". To produce knockouts, using RECOMBINANT DNA technology, the normal DNA sequence of the gene being studied is altered to prevent synthesis of a normal gene product. Cloned cells in which this DNA alteration is successful are then injected into mouse EMBRYOS to produce chimeric mice. The chimeric mice are then bred to yield a strain in which all the cells of the mouse contain the disrupted gene. Knockout mice are used as EXPERIMENTAL ANIMAL MODELS for diseases (DISEASE MODELS, ANIMAL) and to clarify the functions of the genes.Sexual Behavior, Animal: Sexual activities of animals.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.Tissue Distribution: Accumulation of a drug or chemical substance in various organs (including those not relevant to its pharmacologic or therapeutic action). This distribution depends on the blood flow or perfusion rate of the organ, the ability of the drug to penetrate organ membranes, tissue specificity, protein binding. The distribution is usually expressed as tissue to plasma ratios.GABA Antagonists: Drugs that bind to but do not activate GABA RECEPTORS, thereby blocking the actions of endogenous GAMMA-AMINOBUTYRIC ACID and GABA RECEPTOR AGONISTS.Neuronal Plasticity: The capacity of the NERVOUS SYSTEM to change its reactivity as the result of successive activations.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.Mushroom Bodies: Prominent lobed neuropils found in ANNELIDA and all ARTHROPODS except crustaceans. They are thought to be involved in olfactory learning and memory.Adult Stem Cells: Cells with high proliferative and self renewal capacities derived from adults.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.Administration, Intranasal: Delivery of medications through the nasal mucosa.Aldehydes: Organic compounds containing a carbonyl group in the form -CHO.Nose: A part of the upper respiratory tract. It contains the organ of SMELL. The term includes the external nose, the nasal cavity, and the PARANASAL SINUSES.Cell Count: The number of CELLS of a specific kind, usually measured per unit volume or area of sample.Colubridae: The largest family of snakes, comprising five subfamilies: Colubrinae, Natricinae, Homalopsinae, Lycodontinae, and Xenodontinae. They show a great diversity of eating habits, some eating almost anything, others having a specialized diet. They can be oviparous, ovoviviparous, or viviparous. The majority of North American snakes are colubrines. Among the colubrids are king snakes, water moccasins, water snakes, and garter snakes. Some genera are poisonous. (Goin, Goin, and Zug, Introduction to Herpetology, 3d ed, pp321-29)Cell Differentiation: Progressive restriction of the developmental potential and increasing specialization of function that leads to the formation of specialized cells, tissues, and organs.TurtlesBrain Mapping: Imaging techniques used to colocalize sites of brain functions or physiological activity with brain structures.