Reticular Formation: A region extending from the PONS & MEDULLA OBLONGATA through the MESENCEPHALON, characterized by a diversity of neurons of various sizes and shapes, arranged in different aggregations and enmeshed in a complicated fiber network.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.Medulla Oblongata: The lower portion of the BRAIN STEM. It is inferior to the PONS and anterior to the CEREBELLUM. Medulla oblongata serves as a relay station between the brain and the spinal cord, and contains centers for regulating respiratory, vasomotor, cardiac, and reflex activities.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.Cats: The domestic cat, Felis catus, of the carnivore family FELIDAE, comprising over 30 different breeds. The domestic cat is descended primarily from the wild cat of Africa and extreme southwestern Asia. Though probably present in towns in Palestine as long ago as 7000 years, actual domestication occurred in Egypt about 4000 years ago. (From Walker's Mammals of the World, 6th ed, p801)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.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.Wheat Germ Agglutinin-Horseradish Peroxidase Conjugate: The lectin wheatgerm agglutinin conjugated to the enzyme HORSERADISH PEROXIDASE. It is widely used for tracing neural pathways.Consummatory Behavior: An act which constitutes the termination of a given instinctive behavior pattern or sequence.Neuronal Tract-Tracers: Substances used to identify the location and to characterize the types of NEURAL PATHWAYS.Electric Stimulation: Use of electric potential or currents to elicit biological responses.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.Sleep, REM: A stage of sleep characterized by rapid movements of the eye and low voltage fast pattern EEG. It is usually associated with dreaming.Stomatognathic System: The mouth, teeth, jaws, pharynx, and related structures as they relate to mastication, deglutition, and speech.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.Wakefulness: A state in which there is an enhanced potential for sensitivity and an efficient responsiveness to external stimuli.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.Neural Pathways: Neural tracts connecting one part of the nervous system with another.Thalamic Nuclei: Several groups of nuclei in the thalamus that serve as the major relay centers for sensory impulses in the brain.Intralaminar Thalamic Nuclei: Cell groups within the internal medullary lamina of the THALAMUS. They include a rostral division comprising the paracentral, central lateral, central dorsal, and central medial nuclei, and a caudal division composed of the centromedian and parafascicular nuclei.Reticulum: The second stomach of ruminants. It lies almost in the midline in the front of the abdomen, in contact with the liver and diaphragm and communicates freely with the RUMEN via the ruminoreticular orifice. The lining of the reticulum is raised into folds forming a honeycomb pattern over the surface. (From Concise Veterinary Dictionary, 1988)Photomicrography: Photography of objects viewed under a microscope using ordinary photographic methods.Microinjections: The injection of very small amounts of fluid, often with the aid of a microscope and microsyringes.Electroencephalography: Recording of electric currents developed in the brain by means of electrodes applied to the scalp, to the surface of the brain, or placed within the substance of the brain.Vestibular Nuclei: The four cellular masses in the floor of the fourth ventricle giving rise to a widely dispersed special sensory system. Included is the superior, medial, inferior, and LATERAL VESTIBULAR NUCLEUS. (From Dorland, 27th ed)Thalamus: Paired bodies containing mostly GRAY MATTER and forming part of the lateral wall of the THIRD VENTRICLE of the brain.Oculomotor Nerve: The 3d cranial nerve. The oculomotor nerve sends motor fibers to the levator muscles of the eyelid and to the superior rectus, inferior rectus, and inferior oblique muscles of the eye. It also sends parasympathetic efferents (via the ciliary ganglion) to the muscles controlling pupillary constriction and accommodation. The motor fibers originate in the oculomotor nuclei of the midbrain.Trigeminal Nuclei: Nuclei of the trigeminal nerve situated in the brain stem. They include the nucleus of the spinal trigeminal tract (TRIGEMINAL NUCLEUS, SPINAL), the principal sensory nucleus, the mesencephalic nucleus, and the motor nucleus.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.Superior Colliculi: The anterior pair of the quadrigeminal bodies which coordinate the general behavioral orienting responses to visual stimuli, such as whole-body turning, and reaching.Neurons, Efferent: Neurons which send impulses peripherally to activate muscles or secretory cells.Electromyography: Recording of the changes in electric potential of muscle by means of surface or needle electrodes.Abducens Nerve: The 6th cranial nerve which originates in the ABDUCENS NUCLEUS of the PONS and sends motor fibers to the lateral rectus muscles of the EYE. Damage to the nerve or its nucleus disrupts horizontal eye movement control.Immobility Response, Tonic: An induced response to threatening stimuli characterized by complete loss of muscle strength.Stilbamidines: STILBENES with AMIDINES attached.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.Saccades: An abrupt voluntary shift in ocular fixation from one point to another, as occurs in reading.Spinal Cord: A cylindrical column of tissue that lies within the vertebral canal. It is composed of WHITE MATTER and GRAY MATTER.Decerebrate State: A condition characterized by abnormal posturing of the limbs that is associated with injury to the brainstem. This may occur as a clinical manifestation or induced experimentally in animals. The extensor reflexes are exaggerated leading to rigid extension of the limbs accompanied by hyperreflexia and opisthotonus. This condition is usually caused by lesions which occur in the region of the brainstem that lies between the red nuclei and the vestibular nuclei. In contrast, decorticate rigidity is characterized by flexion of the elbows and wrists with extension of the legs and feet. The causative lesion for this condition is located above the red nuclei and usually consists of diffuse cerebral damage. (From Adams et al., Principles of Neurology, 6th ed, p358)Hypoglossal Nerve: The 12th cranial nerve. The hypoglossal nerve originates in the hypoglossal nucleus of the medulla and supplies motor innervation to all of the muscles of the tongue except the palatoglossus (which is supplied by the vagus). This nerve also contains proprioceptive afferents from the tongue muscles.Afferent Pathways: Nerve structures through which impulses are conducted from a peripheral part toward a nerve center.Motor Neurons: Neurons which activate MUSCLE CELLS.Head Movements: Voluntary or involuntary motion of head that may be relative to or independent of body; includes animals and humans.GABA-A Receptor Agonists: Endogenous compounds and drugs that bind to and activate GABA-A RECEPTORS.GABA Agonists: Endogenous compounds and drugs that bind to and activate GAMMA-AMINOBUTYRIC ACID receptors (RECEPTORS, GABA).Thiamylal: A barbiturate that is administered intravenously for the production of complete anesthesia of short duration, for the induction of general anesthesia, or for inducing a hypnotic state. (From Martindale, The Extra Pharmacopoeia, 30th ed, p919)Red Nucleus: A pinkish-yellow portion of the midbrain situated in the rostral mesencephalic tegmentum. It receives a large projection from the contralateral half of the CEREBELLUM via the superior cerebellar peduncle and a projection from the ipsilateral MOTOR CORTEX.Cholinergic Agonists: Drugs that bind to and activate cholinergic receptors.Ophthalmoplegia: Paralysis of one or more of the ocular muscles due to disorders of the eye muscles, neuromuscular junction, supporting soft tissue, tendons, or innervation to the muscles.Arousal: Cortical vigilance or readiness of tone, presumed to be in response to sensory stimulation via the reticular activating system.Stomach, RuminantSleep: A readily reversible suspension of sensorimotor interaction with the environment, usually associated with recumbency and immobility.gamma-Aminobutyric Acid: The most common inhibitory neurotransmitter in the central nervous system.Action Potentials: Abrupt changes in the membrane potential that sweep along the CELL MEMBRANE of excitable cells in response to excitation stimuli.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.Electrooculography: Recording of the average amplitude of the resting potential arising between the cornea and the retina in light and dark adaptation as the eyes turn a standard distance to the right and the left. The increase in potential with light adaptation is used to evaluate the condition of the retinal pigment epithelium.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.Acetylcholine: A neurotransmitter found at neuromuscular junctions, autonomic ganglia, parasympathetic effector junctions, a subset of sympathetic effector junctions, and at many sites in the central nervous system.Functional Laterality: Behavioral manifestations of cerebral dominance in which there is preferential use and superior functioning of either the left or the right side, as in the preferred use of the right hand or right foot.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.Horseradish Peroxidase: An enzyme isolated from horseradish which is able to act as an antigen. It is frequently used as a histochemical tracer for light and electron microscopy. Its antigenicity has permitted its use as a combined antigen and marker in experimental immunology.Anesthesia: A state characterized by loss of feeling or sensation. This depression of nerve function is usually the result of pharmacologic action and is induced to allow performance of surgery or other painful procedures.Macaca fascicularis: A species of the genus MACACA which typically lives near the coast in tidal creeks and mangrove swamps primarily on the islands of the Malay peninsula.Forelimb: A front limb of a quadruped. (The Random House College Dictionary, 1980)Axonal Transport: The directed transport of ORGANELLES and molecules along nerve cell AXONS. Transport can be anterograde (from the cell body) or retrograde (toward the cell body). (Alberts et al., Molecular Biology of the Cell, 3d ed, pG3)Shoulder: Part of the body in humans and primates where the arms connect to the trunk. The shoulder has five joints; ACROMIOCLAVICULAR joint, CORACOCLAVICULAR joint, GLENOHUMERAL joint, scapulathoracic joint, and STERNOCLAVICULAR joint.Macaca mulatta: A species of the genus MACACA inhabiting India, China, and other parts of Asia. The species is used extensively in biomedical research and adapts very well to living with humans.Bicuculline: An isoquinoline alkaloid obtained from Dicentra cucullaria and other plants. It is a competitive antagonist for GABA-A receptors.Locomotion: Movement or the ability to move from one place or another. It can refer to humans, vertebrate or invertebrate animals, and microorganisms.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.Neural Inhibition: The function of opposing or restraining the excitation of neurons or their target excitable cells.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.Solitary Nucleus: GRAY MATTER located in the dorsomedial part of the MEDULLA OBLONGATA associated with the solitary tract. The solitary nucleus receives inputs from most organ systems including the terminations of the facial, glossopharyngeal, and vagus nerves. It is a major coordinator of AUTONOMIC NERVOUS SYSTEM regulation of cardiovascular, respiratory, gustatory, gastrointestinal, and chemoreceptive aspects of HOMEOSTASIS. The solitary nucleus is also notable for the large number of NEUROTRANSMITTERS which are found therein.Reflex: An involuntary movement or exercise of function in a part, excited in response to a stimulus applied to the periphery and transmitted to the brain or spinal cord.Cerebellum: The part of brain that lies behind the BRAIN STEM in the posterior base of skull (CRANIAL FOSSA, POSTERIOR). It is also known as the "little brain" with convolutions similar to those of CEREBRAL CORTEX, inner white matter, and deep cerebellar nuclei. Its function is to coordinate voluntary movements, maintain balance, and learn motor skills.Injections: Introduction of substances into the body using a needle and syringe.Reticulin: A scleroprotein fibril consisting mostly of type III collagen. Reticulin fibrils are extremely thin, with a diameter of between 0.5 and 2 um. They are involved in maintaining the structural integrity in a variety of organs.Carbachol: A slowly hydrolyzed CHOLINERGIC AGONIST that acts at both MUSCARINIC RECEPTORS and NICOTINIC RECEPTORS.Startle Reaction: A complex involuntary response to an unexpected strong stimulus usually auditory in nature.Cerebral Cortex: The thin layer of GRAY MATTER on the surface of the CEREBRAL HEMISPHERES that develops from the TELENCEPHALON and folds into gyri and sulchi. It reaches its highest development in humans and is responsible for intellectual faculties and higher mental functions.
Caudal pontine reticular nucleus: The caudal pontine reticular nucleus or nucleus reticularis pontis caudalis is composed of gigantocellular neurons.Medial lemniscus: The medial lemniscus, also known as Reil's band or Reil's ribbon, is a large ascending bundle of heavily myelinated axons that decussate in the brain stem, specifically in the medulla. The medial lemniscus is formed by the crossings of internal arcuate fibers.Rostral ventromedial medulla: The rostral ventromedial medulla (RVM), or ventromedial nucleus of the spinal cord, is a group of neurons located close to the midline on the floor of the medulla oblongata (myelencephalon). The rostral ventromedial medulla sends descending inhibitory and excitatory fibers to the dorsal horn spinal cord neurons.Central tegmental tract: The central tegmental tractKamali A, Kramer LA, Butler IJ, Hasan KM. Diffusion tensor tractography of the somatosensory system in the human brainstem: initial findings using high isotropic spatial resolution at 3.Cats in the United States: Many different species of mammal can be classified as cats (felids) in the United States. These include domestic cat (both house cats and feral), of the species Felis catus; medium-sized wild cats from the genus Lynx; and big cats from the genera Puma and Panthera.Lipoatrophia semicircularis: Lipoatrophia semicircularis (also known as semicircular lipoatrophy) is a medical condition in humans, commonly known as ribbed thighs.Cortical stimulation mapping: Cortical stimulation mapping (often shortened to CSM) is a type of electrocorticography that involves a physically invasive procedure and aims to localize the function of specific brain regions through direct electrical stimulation of the cerebral cortex. It remains one of the earliest methods of analyzing the brain and has allowed researchers to study the relationship between cortical structure and systemic function.Pedunculopontine nucleus: The pedunculopontine nucleus (PPN) (or pedunculopontine tegmental nucleus, PPTN or PPTg) is located in the brainstem, caudal to the substantia nigra and adjacent to the superior cerebellar peduncle. It has two divisions, one containing cholinergic neurons, the pars compacta, and one containing mostly glutamatergic neurons, the pars dissipata.HSD2 neurons: HSD2 neurons are a small group of neurons in the brainstem which are uniquely sensitive to the mineralocorticosteroid hormone aldosterone, through expression of HSD11B2. They are located within the caudal medulla oblongata, in the nucleus of the solitary tract (NTS).Laterodorsal tegmental nucleus: The laterodorsal tegmental nucleus (or lateroposterior tegmental nucleus) is a nucleus situated in the brainstem, spanning the midbrain tegmentum and the pontine tegmentum. Its location is one-third of the way from the pedunculopontine nucleus to the thalamus, inferior to the pineal gland.Intralaminar nuclei of thalamus: The intralaminar nuclei are collections of neurons in the thalamus that are generally divided in two groups as follows:Mancall, E., Brock, D.Reticulum (anatomy): The reticulum is the first chamber in the alimentary canal of a ruminant animal. Anatomically it is considered the smaller portion of the reticulorumen along with the rumen.Jesse Mitchell: Captain Jesse Mitchell was a British army officer who served as Superintendent of the Government Museum, Madras, succeeding Edward Balfour, from 15 May 1859 to 7 August 1872. He was one of the pioneers of photomicrography in India.Quantitative electroencephalography: Quantitative electroencephalography (QEEG) is a field concerned with the numerical analysis of electroencephalography data and associated behavioral correlates.Medial vestibular nucleus: The medial vestibular nucleus is one of the vestibular nuclei. It is located in the medulla oblongata.Oculomotor nucleus: The fibers of the oculomotor nerve arise from a nucleus in the midbrain, which lies in the gray substance of the floor of the cerebral aqueduct and extends in front of the aqueduct for a short distance into the floor of the third ventricle. From this nucleus the fibers pass forward through the tegmentum, the red nucleus, and the medial part of the substantia nigra, forming a series of curves with a lateral convexity, and emerge from the oculomotor sulcus on the medial side of the cerebral peduncle.Mesencephalic nucleus of trigeminal nerve: The mesencephalic nucleus is involved with proprioception of the face, that is, the feeling of position of the muscles. Unlike many nuclei within the central nervous system (CNS), the mesencephalic nucleus contains no chemical synapses but are electrically coupled.Fixation reflex: The fixation reflex is that concerned with attracting the eye on a peripheral object. For example, when a light shines in the periphery, the eyes shift gaze on it.Aging movement control: Normal aging movement control in humans is about the changes on the muscles, motor neurons, nerves, sensory functions, gait, fatigue, visual and manual responses, in men and women as they get older but who do not have neurological, muscular (atrophy, dystrophy...) or neuromuscular disorder.Abducens nucleus: The abducens nucleus is the originating nucleus from which the abducens nerve (VI) emerges - a cranial nerve nucleus. This nucleus is located beneath the fourth ventricle in the caudal portion of the pons, medial to the sulcus limitans.Gordon G. Gallup: Gordon G. Gallup, Jr.HydroxystilbamidineSaccade: A saccade ( , French for jerk) is quick, simultaneous movement of both eyes between two phases of fixation in the same direction.Cassin, B.Neuromere: Neuromeres are morphologically or molecularly defined transient segments of the early developing brain. Rhombomeres are such segments that make up the rhombencephalon or hindbrain.DecerebrationHypoglossal trigone: In the upper part of the medulla oblongata, the hypoglossal nucleus approaches the rhomboid fossa, where it lies close to the middle line, under an eminence named the hypoglossal trigone.Renshaw cell: Renshaw cells are inhibitory interneurons found in the gray matter of the spinal cord, and are associated in two ways with an alpha motor neuron.Fall Heads Roll: Fall Heads Roll is an album by The Fall, released in 2005. It was recorded at Gracieland Studios in Rochdale, UK and Gigantic Studios in New York, NY.ThiamylalOphthalmoparesisLow arousal theory: Low arousal}}Non-rapid eye movement sleepPivagabineVentricular action potentialSuvorexantElectrooculographyCerebral hemisphere: The vertebrate cerebrum (brain) is formed by two cerebral hemispheres that are separated by a groove, the medial longitudinal fissure. The brain can thus be described as being divided into left and right cerebral hemispheres.Serotonergic cell groups: Serotonergic cell groups refer to collections of neurons in the central nervous system that have been demonstrated by histochemical fluorescence to contain the neurotransmitter serotonin (5-hydroxytryptamine). Since they are for the most part localized to classical brainstem nuclei, particularly the raphe nuclei, they are more often referred to by the names of those nuclei than by the B1-9 nomenclature.Horseradish peroxidaseAnesthesia cart: Anesthesia carts are hospital devices used to store tools that are necessary for aid during procedures that require administration of anesthesia. Anesthesia refers to the use of drugs to subdue a patient's mind and prevent him or her from feeling any pain during a surgical operation.Nephtheis fascicularisAxoplasmic transport: Axoplasmic transport, also called axonal transport, is a cellular process responsible for movement of mitochondria, lipids, synaptic vesicles, proteins, and other cell parts (i.e.BicucullineWalker (BEAM): In BEAM robotics, a walker is a walking machine that has a driven mode of locomotion by intermittent ground-contacting legs. They usually possess 1 to 12 (generally, three or less) motors.Solitary nucleus: In the human brain, the solitary nucleus (nucleus of the solitary tract, nucleus solitarius, nucleus tractus solitarii, NTS) is a series of nuclei (clusters of nerve cell bodies) forming a vertical column of grey matter embedded in the medulla oblongata. Through the center of the NTS runs the solitary tract, a white bundle of nerve fibers, including fibers from the facial, glossopharyngeal and vagus nerves, that [the NTS.Withdrawal reflex: The withdrawal reflex (nociceptive or flexor withdrawal reflex) is a spinal reflex intended to protect the body from damaging stimuli. It is polysynaptic, causing stimulation of sensory, association, and motor neurons.Inferior cerebellar peduncle: The upper part of the posterior district of the medulla oblongata is occupied by the inferior cerebellar peduncle (restiform body), a thick rope-like strand situated between the lower part of the fourth ventricle and the roots of the glossopharyngeal and vagus nerves.Reticular fiber: Reticular fibers, reticular fibres or reticulin is a type of fiber in connective tissue composed of type III collagen secreted by reticular cells. Reticular fibers crosslink to form a fine meshwork (reticulin).SonepiprazoleTBR1: T-box, brain, 1 is a transcription factor protein important in vertebrate embryo development. It is encoded by the TBR1 gene.
(1/389) Correlation of primate superior colliculus and reticular formation discharge with proximal limb muscle activity.
We studied the discharge of neurons from both the superior colliculus (SC) and the underlying mesencephalic reticular formation (MRF) and its relation to the simultaneously recorded activity of 11 arm muscles. The 242 neurons tested with a center-out reach task yielded 2,586 pairs of neuron/muscle cross-correlations (normalized, such that perfect correlations are +/-1.0). Of these, 43% had peaks with magnitude as large as 0.15, a value that corresponds to the 5% level of significance, and 16% were as large as 0.25. The great majority of peaks in this latter group was positive. The median lag time within this group was 52 ms, indicating that the neuronal discharge tended to precede the correlated muscle activity. We found a small but significantly higher proportion of cells with these relatively strong correlations in the MRF than in the SC. For both areas, these occurred most frequently with muscles of the shoulder girdle and became less frequent for axial as well as for increasingly distal arm musculature. The results support a role for the SC and MRF in guiding the arm during reach movements via the control of proximal limb musculature. (+info)
(2/389) Clonidine evokes vasodepressor responses via alpha2-adrenergic receptors in gigantocellular reticular formation.
The gigantocellular depressor area (GiDA) is a functionally defined subdivision of the medullary gigantocellular reticular formation where vasodepressor responses are evoked by glutamate nanoinjections. The GiDA also contains reticulospinal neurons that contain the alpha2A-adrenergic receptor (alpha2A-AR). In the present study, we sought to determine whether nanoinjections of the alpha2-AR agonist clonidine into the GiDA evoke cardiovascular responses and whether these responses can be attributed to the alpha2-AR. We found that nanoinjections of clonidine into the GiDA evoke dose-dependent decreases in arterial pressure and heart rate. These responses were equivalent in magnitude to responses produced by clonidine nanoinjections into the sympathoexcitatory region of the rostral ventrolateral medulla. Furthermore, the vasodepressor and bradycardic responses produced by clonidine injections into the GiDA were blocked in a dose-dependent fashion by the highly selective alpha2-AR antagonist 2-methoxyidazoxan, but not by prazosin, which is an antagonist at both the alpha1-AR and the 2B subtype of the alpha-AR. The antagonism by 2-methoxyidazoxan was site specific because injections of the antagonist into the rostral ventrolateral medulla failed to block the responses evoked by clonidine injections into the GiDA. These findings support the notion that clonidine produces sympathoinhibition through multiple sites within the medullary reticular formation, which is consistent with the wide distribution of the alpha2A-AR in reticulospinal neurons. These data also suggest that clonidine may have multiple mechanisms of action because it evokes a cardiovascular depressive response from regions containing neurons that have been determined to be both sympathoinhibitory and sympathoexcitatory. (+info)
(3/389) Vasoactive intestinal polypeptide excites medial pontine reticular formation neurons in the brainstem rapid eye movement sleep-induction zone.
Although it has long been known that microinjection of the cholinergic agonist carbachol into the medial pontine reticular formation (mPRF) induces a state that resembles rapid eye movement (REM) sleep, it is likely that other transmitters contribute to mPRF regulation of behavioral states. A key candidate is the peptide vasoactive intestinal polypeptide (VIP), which innervates the mPRF and induces REM sleep when injected into this region of the brainstem. To begin understanding the cellular mechanisms underlying this phenomenon, we examined the effects of VIP on mPRF cells using whole-cell patch-clamp recordings in the in vitro rat brainstem slice. VIP directly depolarized cells via activation of an inward current; these effects were attenuated and potentiated in low-sodium and low-calcium medium, respectively. The depolarization induced by VIP was slower in onset and longer-lived than that evoked by carbachol. The VIP-induced depolarization was reduced in a dose-dependent manner by a competitive antagonist of VIP receptors. Effects of VIP were attenuated in the presence of guanosine 5'-O-(2-thiodiphosphate, 2'5'dideoxyadenosine, and PKI15-24 and were nonadditive in the presence of 8-bromo-cAMP. We conclude that VIP excites mPRF neurons by activation of a sodium current. This effect is mediated at least in part by G-protein stimulation of adenylyl cyclase, cAMP, and protein kinase A. These data suggest that VIP may play a physiological role in REM induction by its actions on mPRF neurons. (+info)
(4/389) Fos-like immunoreactivity in the brain stem following oral quinine stimulation in decerebrate rats.
The present study compared the distribution of Fos-like immunoreactivity (FLI) following intraoral stimulation with quinine monohydrochloride (QHCl) in awake intact rats to the pattern obtained in chronic supracollicular decerebrate (CD) rats. Because the behavioral rejection response to QHCl is evident in the CD rat, it was hypothesized that the pattern of FLI in the lower brain stem should be similar in both groups. Overall, the distribution of FLI in the brain stem was quite similar in both intact and CD groups, and QHCl stimulation increased FLI in the rostral (gustatory) nucleus of the solitary tract, the parabrachial nucleus (PBN), and the lateral reticular formation (RF) compared with an unstimulated control group. The CD group differed from the intact group, however, with a trend toward less FLI in the RF and a shift in the pattern of label away from the external subdivision of the PBN. CD rats also had increased FLI in the caudal nucleus of the solitary tract, with or without intraoral infusions. The distribution of QHCl-induced FLI in the brain stem of intact rats thus indicates both local sensorimotor processing as well as the influence of forebrain structures. (+info)
(5/389) Fluorescent double-label study of lateral reticular nucleus projections to the spinal cord and periaqueductal gray in the rat.
Following injections of WGA-HRP into either the spinal cord or periaqueductal gray, labeled neurons were observed bilaterally along the periphery of the lateral reticular nucleus (LRN) magnocellular division. The possibility that some of these neurons in the LRN provide collateral axonal branches to both the periaqueductal gray and the spinal cord was investigated in rats using a retrograde double-labeling method employing two different fluorescent tracers, True Blue and Nuclear Yellow. Following sequential injection of the two fluorescent axonal tracers into the spinal cord and periaqueductal gray in the same animal, a modest number of double-labeled neurons were observed bilaterally near the medial and dorsal perimeter of the magnocellular division of the LRN. The labeled neurons were distinctly multipolar in shape and measured approximately 15-18 mu in their greatest transverse diameter. No double-labeled neurons were observed in the parvocellular or subtrigeminal divisions of the LRN. Based upon these observations, it is suggested that collaterals of the LRN-spinal pathway provide feedback information to the periaqueductal gray that might then be used to modulate the participation of the latter cell group in a variety of pain processing and cardiovascular regulatory functions. (+info)
(6/389) Mauthner and reticulospinal responses to the onset of acoustic pressure and acceleration stimuli.
We determined how the Mauthner cell and other large, fast-conducting reticulospinal neurons of the goldfish responded to acoustic stimuli likely to be important in coordinating body movements underlying escape. The goal was to learn about the neurophysiological responses to these stimuli and the underlying processes of sensorimotor integration. We compared the intracellularly recorded postsynaptic responses (PSPs) of 9 Mauthner cells and a population of 12 other reticulospinal neurons to acoustic pressure and acceleration stimuli. All recorded cells received both pressure and acceleration inputs and responded to stimuli regardless of initial polarity. Thus these cells receive acoustic components necessary to determine source direction. We observed that the Mauthner cell was broadly tuned to acoustic pressure from 100 to 2,000 Hz, with a Q(10dB) of 0.5-1.1 over the best frequency range, 400-800 Hz. This broad tuning is probably due to input from S1 afferents and is similar to tuning of the behavioral audiogram. Our data suggest that cells have relatively more sustained responses to acceleration than to pressure stimuli, to which they rapidly adapted. For a given cell, PSP latencies and amplitudes varied inversely with stimulus intensity. For the entire population of cells studied, minimum onset latencies (i.e., those at the highest intensities) ranged from 0.7 to 7.6 ms for acoustic pressure and 0.7 to 9.8 ms for acceleration. This distribution in minimum onset latencies is consistent with earlier EMG and kinematic findings and supports our previous hypothesis that escape trajectory angle is controlled, in part, by varying the activation time of neurons in the escape network. While the Mauthner cell latency did not differ to both onset polarities of pressure and acceleration, this was not true of all cells. Also, the Mauthner cell responses to pressure were approximately 0.6 ms faster than to acceleration; for the other cells, this difference was 1.1 ms with some cells having differences =3 ms. To both pressure and acceleration, the average, minimum Mauthner cell latency was approximately 1 ms faster than the average of the 12 other cells. These data are consistent with the hypothesis that the Mauthner cell fires first, followed by other reticulospinal neurons, which more finely regulate escape trajectory. Finally, analysis of our results suggests that while pressure is more important in depolarizing the cell near threshold, high levels of acceleration, perhaps from fluid flow, may be very important in activating the system in a directional manner. (+info)
(7/389) Divergence of lamina VII and VIII neurones of S1 and S2 segments of the cat's spinal cord to the cerebellum and the reticular formation.
Cerebellar and reticular projections of neurones located in sacral segments of the spinal cord were electrophysiologically investigated in alpha-chloralose anaesthetized cats. Antidromic action potentials were recorded following stimulation of the contralateral restiform body (coRB), contralateral gigantocellular nucleus (coGRN) as well as ipsi- and contralateral lateral funiculus of the 13th thoracic segment (iTh13 and coTh13). Eighty-seven neurones were found in the medial lamina VII and lamina VIII of the gray matter of S1 and S2 segments. Their axons ascended in lateral funiculi on the contralateral side and in 46 cases also on the ipsilateral side of the spinal cord. A projection to coRB was found in 20 neurones, to coGRN in 10 and dual projections to both coRB and coGRN in 20 neurones. Axons of the remaining 37 cells were found to ascend to the level of Th13 only. Conduction velocities of neurones investigated were comprised in the range 35-83 m/s and no significant differences were found between particular groups. However, an evident decrease in conduction was observed in most neurones when comparing proximal to distal parts of their axons, suggesting the possibility of more extensive divergence than indicated in this study. The pattern of projections revealed that the information from the periphery is conveyed in parallel to various supraspinal and possibly also spinal centres. (+info)
(8/389) Increased gamma- and decreased delta-oscillations in a mouse deficient for a potassium channel expressed in fast-spiking interneurons.
Kv3.1 is a voltage-gated, fast activating/deactivating potassium (K(+)) channel with a high-threshold of activation and a large unit conductance. Kv3.1 K(+) channels are expressed in fast-spiking, parvalbumin-containing interneurons in cortex, hippocampus, striatum, the thalamic reticular nucleus (TRN), and in several nuclei of the brain stem. A high density of Kv3.1 channels contributes to short-duration action potentials, fast afterhyperpolarizations, and brief refractory periods enhancing the capability in these neurons for high-frequency firing. Kv3.1 K(+) channel expression in the TRN and cortex also suggests a role in thalamocortical and cortical function. Here we show that fast gamma and slow delta oscillations recorded from the somatomotor cortex are altered in the freely behaving Kv3.1 mutant mouse. Electroencephalographic (EEG) recordings from homozygous Kv3.1(-/-) mice show a three- to fourfold increase in both absolute and relative spectral power in the gamma frequency range (20-60 Hz). In contrast, Kv3.1-deficient mice have a 20-50% reduction of power in the slow delta range (2-3 Hz). The increase in gamma power is most prominent during waking in the 40- to 55-Hz range, whereas the decrease in delta power occurs equally across all states of arousal. Our findings suggest that Kv3. 1-expressing neurons are involved in the generation and maintenance of cortical fast gamma and slow delta oscillations. Hence the Kv3. 1-mutant mouse could serve as a model to study the generation and maintenance of fast gamma and slow delta rhythms and their involvement in behavior and cognition. (+info)