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S T Kitai

Publications and source records attributed to S T Kitai.

At least 127 records · Page 7Linked to original sources
PubMed1981

Single neostriatal efferent axons in the globus pallidus: a light and electron microscopic study.

Intracellularly labeled rat neostriatal projection neurons were analyzed with both light and electron microscopy. The axons of medium spiny neurons were traced into the globus pallidus and were found to make synaptic contacts with pallidal dendrites. Despite the common somato-dendritic morphology of the neostriatal projection neurons, two different distribution patterns of efferent axons were observed, indicating the presence of functionally different medium spiny neurons in the neostriatum.

Animals↗
PubMed1981

Anatomy and physiology of the neostriatum.

The Fig. 9 is a summary of the synaptic relations of various neuronal elements of the neostriatum. Striatal neurons receive convergent excitatory inputs from the cerebral cortex, the intralaminar thalamus, the substantia nigra (pars compacta) and the dorsal raphe nucleus. The striatal projection neurons are numerous and medium spiny neurons are at least one type of projection neurons which receive direct convergent excitation from extrinsic afferents. The resultant influence of this excitation is directed, in turn, not only to extra-striatal target neurons, but also extensively to cells within the neostriatum. The action of the medium spiny projection neurons is inhibitory and most likely GABA-ergic.

Afferent Pathways↗
PubMed1980

Recurrent inhibition in the rat neostriatum.

During intracellular recording, in the neostriatum of rats anesthetized with urethane, the triggering of an action potential in the recorded neuron by a depolarizing pulse of current resulted in inhibition in that same neuron. This inhibition was evident through its ability to reduce the amplitude of EPSPs evoked from stimulation of substantia nigra. The shunting of SN EPSPs was shown not to be due to action potential currents. The inhibition is antagonized by the GABA blocking agent bicuculline. Intracellular labeling of recorded neurons revealed them as medium spiny neurons. It is concluded that the extensive axon collaterals of spiny projection neurons mediate recurrent inhibition, a portion of which involves autaptic synapses of a neuron back onto itself.

Animals↗
PubMed1980

Medium spiny neuron projection from the rat striatum: an intracellular horseradish peroxidase study.

The morphological features of striatal projection neurons and the responses of these neurons to electrical stimulation of the substantia nigra were studied in rats through the methods of intracellular recording and intracellular labeling with the enzyme horseradish peroxidase. Under urethane anesthesia, single striatal neurons were first analyzed for responsiveness to nigral stimuli and then filled electrophoretically with the enzyme in order to permit subsequent serial reconstruction. The axon of the medium spiny neuron was found to form an extensive collateral plexus within the striatum before entering the globus pallidus or the internal capsule. These medium spiny projection neurons responded to nigral stimuli with monosynaptic excitation.

Animals↗
PubMed1979

An HRP and autoradiographic study of the projection from the cerebellar cortex to the nucleus interpositus anterior and nucleus interpositus posterior of the cat.

The recently developed anatomical techniques of retrograde transport of the enzyme horseradish peroxidase (HRP), anterograde transport of tritiated amino acid, and intracellular injections of HRP were used to study the organization of the corticonuclear projection to the nucleus interpositus anterior (NIA) and the nucleus interpositus posterior (NIP) of the cat. Injections of HRP into the NIA and the NIP revealed that the major areas of the cortex which provided afferents to these two nuclei were the intermediate cortex of the anterior lobe (IAL) and the paramedian lobule (PML). There were, however, significant differences in the distribution of Purkinje (Pk) cells which projected to each nucleus. The NIA received afferents from all areas of the IAL while the NIP projection area was restricted to a band located at the medi-almost aspect of the lobe. All areas of the PML, in particular the intermediate folia, projected to the NIP, while the Pk cells which sent axons to the NIA were restricted to the rostral and caudal folia of this lobule. The projection from each area was somatotopically organized. The axons of intracellularly stained Pk cells were followed to their termination in the NIA and NIP confirming the results obtained with the two extracellular techniques. An attempt was made to examine the organization of the corticonuclear projection at the single cell level in the PML. Pk cells located in the same sagittal plane appeared to terminate in the same area of the same nucleus while Pk cells located not more than 500 micrometers medial or lateral to each other terminated in different nuclei. Basically, the organization of the corticonuclear projection from the IAL is longitudinally organized while the PML has a much more complex arrangement in which the Pk cells projecting to the NIA and NIP are interspersed.

Amino Acids↗
PubMed1978

Morphological and electrophysiological characteristics of projection neurons in the nucleus interpositus of the cat cerebellum.

The populations of neurons in the nucleus interpositus (IP) of the cat cerebellum which project to the ventral lateral nucleus of the thalamus (VL), the red nucleus (RN), the nucleus reticularis tegmenti pontis (NRTP), the pontine nuclei (PN), the inferior olive (IO), and the cerebellar cortex were identified by intracellular and extracellular injections of HRP and studied electrophysiologically. When HRP was simultaneously injected into the VL, RN, and IO, over 95% of the neurons in the IP nuclei were labeled; indicating that there are few, if any, local circuit neurons. The vast majority (86%) of the larger IP neurons (soma length greater than or equal to 20 micrometer) project rostrally to the RN and thalamus. These neurons typically have long, relatively spine free dendrites and axons which in a few cases gave rise to recurrent collaterals. Two intracellularly stained projection neurons which had exceptionally long spiny dendrites had axons which gave rise to nucleocortical collaterals in addition to several local collaterals. IP neurons projecting to the NRTP and PN were located primarily in the lateral aspect of the nucleus interpositus anterior. Electrophysiological experiments established that neurons projecting to the NRTP also project to the VL. The IP neurons projecting to the IO have small fusiform or multipolar somata, long thin dendrites, and receive excitatory inputs from the IO. At least 73% of the small neurons in the IP project to the IO, and some of these, in addition, project to the VL. There are at least three morphologically distinguishable populations of projection neurons, small IO projections neurons, and neurons with nucleocortical collaterals. The projection of the IP to diverse regions of the brain is accomplished mainly by axon collateralization, but regional and morphological specialization also play a role in the organization of the output of the IP.

Animals↗
PubMed1978

Response properties and electrical constants of caudate nucleus neurons in the cat.

1. Response properties and passive electrical constants were assessed for caudate nucleus neurons in pentobarbital-anesthetized cats. The neurons studied were those which could be monosynaptically excited by substantia nigra and thalamic (centromedian-parafascicular) stimulation. 2. Input resistance and membrane time constant were estimated from the plateau value and time course, respectively, of the neuronal membrane response to intracellularly applied current pulses. The average values obtained were 16.5 Momega and 11.3 ms. Specific resistance and capacitance values were calculated. 3. Single or repetitive spikes were readily evoked by nigral or thalamic stimuli or by the application of direct depolarizing currents. Spike thresholds were higher for direct than for synaptic activation (7.2 vs. 5.6 mV). 4. Direct depolarizing stimuli with durations up to 600 ms elicited repetitive discharge with little adaptation of firing rate. The maximum discharge rates induced by direct stimuli were near 200 spikes per second. 5. The intracellular application of tetraethylammonium chloride (TEA) produced spike-prolongation effects in caudate neurons that were similar to the effects reported for other nerve membrane. 6. The probable identity of the recorded neurons as medium spiny neurons was discussed and, in addition, it was proposed that the characteristic silence of these cells is not likely due to intrinsic membrane specialization.

Action Potentials↗
PubMed1977

Dual excitatory inputs to caudate spiny neurons from substantia nigra stimulation.

In the present set of experiments of two component excitatory postsynaptic potential (EPSP) (fast and slow) was recorded from caudate (Cd) neurons after substantia nigra (SN) stimulation in the alpha-chloralose anesthetized cat. Several unique properties of the fast response are demonstrated and used to determine certain functional properties of Cd neurons. The following conclusions have been drawn from these experiments. (1) A dual excitatory innervation pattern (fast and slow) exists to the Cd from SN stimulation. (2) The fast system is independent of the Cd efferent system. (3) Neurons receiving this dual input are spine laden neurons. (4) Dendritic inhibition is operating on these neurons and often has little or no direct influence on the observed soma membrane potential. The dendritic inhibition reduced test EPSP amplitude for several hundred milliseconds for all Cd afferents except for the fast SN input. Such a decoupling of the fast input from the inhibition may play an important role in Cd signal processing.

Afferent Pathways↗
PubMed1977

Convergence of excitatory synaptic inputs to caudate spiny neurons.

Intracellular recordings were obtained from cat caudate nucleus neurons. These cells responded with convergent, monosynaptic EPSPs to cerebral cortex, intralaminar thalamus, and substantia nigra stimulation. Intracellular injection of horseradish peroxidase into these electrophysiologically defined neurons shows that they represent the spiny neuron of the caudate based upon somadendritic morphology. The axons of these cells are appreciably longer than previous reports indicate. Several lines of evidence are discussed to question the intrinsic nature of these neurons.

Animals↗
PubMed1977

Electrophysiological and horseradish peroxidase studies of precerebellar afferents to the nucleus interpositus anterior. I. Climbing fiber system.

The input to the nucleus interpositus anterior (NIA) of the cat from the inferior olive (IO) was studied by stimulating the IO while recording intracellularly from the NIA, and by the retrograde transport of horseradish peroxidase (HRP). Stimulation of the IO evoked monosynaptic EPSPs in NIA neurons. The cells labeled in the IO following electrophoretic and pressure injection of HRP into NIA were located in the rostral parts of the dorsal and medial accessory olive. Stimulation of the IO also polysynaptically evoked an IPSP and a late disinhibitory depolarization. Data were presented which indicated that these potentials were mediated by the Purkinje cells of the cerebellar cortex.

Afferent Pathways↗
PubMed1977

Electrophysiological and horseradish peroxidase studies of precerebellar afferents to the nucleus interpositus anterior. II. Mossy fiber system.

Inputs to the nucleus interpositus anterior (NIA) of the cat from precerebellar nuclei which are thought to give rise to mossy fibers were studied using electrophysiological and anatomical techniques. Stimulation of one of these precerebellar nuclei, the lateral reticular nucleus (LRN) evoked monosynaptic EPSPs in NIA neurons. These EPSPs were followed by polysynaptic IPSPs and late depolarization mediated by the response of the cerebellar cortex. Similar responses were occasionally seen following stimulation of the brachium pontis (BP). When horseradish peroxidase was injected into the NIA, labeled cells were found in the magnocellular and parvicellular LRN, the external cuneate nucleus (ECN), the pontine nuclei and the perihypoglossal nuclei. There was no evidence for a direct projection of the nucleus reticularis pontis to the NIA. It was suggested that most of the tonic excitation of NIA neurons is provided by the LRN and ECN.

Afferent Pathways↗