Corticofugal influences on pontine unit activity

Unit responses of the nuclei pontis (NP) and reticular pontine nuclei (RPN) to stimulation of the frontobasal cortex (proreal, orbital, and basal temporal regions) and of the dorsal hippocampus were studied in cats. Stimulation of the various cortical structures was found to induce phasic and (less frequently) tonic responses in neurons of NP and RPN. The main type of unit response in RPN was primary excitation, whereas in NP it was primary inhibition. The largest number of responding neurons in the pontine nuclei was observed to stimulation of the proreal gyrus. In the cerebro-cerebellar relay system neurons of the reticular tegmental nucleus and ventromedial portion of NP showed the highest ability to respond. In the oral and caudal reticular pontine nuclei the regions of predominant influence of cortical structures were located in zones of these nuclei where neurons with rostral and (to a lesser degree) caudal projections were situated.M. Gorkii Donetsk Medical Institute. Translated from Neirofiziologiya, Vol. 12, No. 4, pp. 358–367, July–August, 1980.     

Neuronal responses of the reticular and anterior ventral thalamic nuclei to stimulation of the thalamic ventrolateral nucleus and motor cortex

Responses of 137 neurons of the rostral pole of the reticular and anterior ventral thalamic nuclei to electrical stimulation of the ventrolateral nucleus and motor cortex were studied in 17 cats immobilized with D-tubocurarine. The number of neurons responding antidromically to stimulation of the ventrolateral nucleus was 10.5% of all cells tested (latent period of response 0.7–3.0 msec), whereas to stimulation of the motor cortex it was 11.0% (latent period of response 0.4–4.0 msec). Neurons with a dividing axon, one branch of which terminated in the thalamic ventrolateral nuclei, the other in the motor cortex, were found. Orthodromic excitation was observed in 78.9% of neurons tested during stimulation of the ventrolateral nucleus and in 52.5% of neurons during stimulation of the motor cortex. Altogether 55.6% of cells responded to stimulation of the ventrolateral nucleus with a discharge of 3 to 20 action potentials with a frequency of 130–350 Hz. Similar discharges in response to stimulation of the motor cortex were observed in 30.5% of neurons tested. An inhibitory response was recorded in only 6.8% of cells. Convergence of influences from the thalamic ventrolateral nucleus and motor cortex was observed in 55.7% of neurons. The corticofugal influence of the motor cortex on responses arising in these cells to testing stimulation of the ventrolateral nucleus could be either inhibitory or facilitatory.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 10, No. 5, pp. 460–468, September–October, 1978.     

Effect of reticular formation on hippocampal neurons (field CA1)

The reaction of field CA₁ hippocampal neurons to stimulation of the reticular formation (RF) with impulses of different frequencies was investigated in experiments on unanesthetized rabbits. The effect of electrical and sensory stimuli was compared and the effect of reticular stimulation on the sensory responses was determined. With an increase in the frequency of RF stimulation, the number of neurons of field CA₁ responding with inhibition of the activity increases. Multimodal neurons of the hippocampus depend on the reticular input to a greater degree than unimodal neurons. Neurons whose activity does not change in response to the effect of sensory stimuli also do not respond to stimulation of the RF. Neurons responding with inhibitory reactions to sensory stimulation show a higher correlation with the effects of RF stimulation than neurons with activation reactions and, especially those with "complex" responses to the effect of sensory stimuli. In a considerable number of hippocampal neurons the responses to sensory stimuli change in the course of 10–15 min after stimulation of the RF. The role of the RF in the organization of the reactions of hippocampal neurons is discussed.Division of Memory Problems, Institute of Biological Physics, Academy of Sciences of the USSR, Pushchino-on-Oke. Translated from Neirofiziologiya, Vol. 3, No. 3, pp. 227–235, May–June, 1971.     

Reticular pathways transmitting corticofugal impulses

Details of the organization of reticular pathways transmitting motor cortical influences were studied in cats anesthetized with chloralose. Of all reticular neurons studied 33.3% were reticulospinal cells, 12.2% were neurons with descending-ascending projection of their axons, 15.4% were purely ascending neurons, and 39.1% were unidentified cells. Analysis of responses evoked by cortical stimulation showed that influences of both fast- and slowly-conducting corticofugal fibers are transmitted through reticulospinal cells, neurons with descending-ascending projections, and cells projecting into the hypothalamus. It was shown that 37% of reticulospinal and 66.7% of neurons with two-way projection that were studied form a group of cells transmitting rapidly into the spinal cord impulses from slowly-conducting fibers only. Reticular neurons with projections to the thalamus also transmit influences of slowly-conducting fibers only. The organization and role of reticular pathways transmitting corticogugal impulses are discussed.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 13, No. 5, pp. 491–499, September–October, 1981.     

Effect of local cooling of the cortex on evoked potentials in the reticular formation in response to somatosensory stimulation

Potentials evoked in nuclei of the reticular formation by electrodermal stimulation of the limbs were investigated in acute experiments on unanesthetized, immobilized rats during cooling of the somatosensory cortex in the area of representation of one forelimb. Evoked potentials in the reticular formation were found to depend on the degree of cold inhibition of the cortical primary response to the same stimulation. The peak time of the main negative wave increased from 40–50 to 60–80 msec with a simultaneous decrease in its amplitude or its total disappearance in the case of deep cooling of the cortex. Cooling of the cortex had a similar although weaker effect on the earlier wave of the evoked potential with a peak time of 14 msec, recorded in the ventral reticular nucleus. In parallel recordings of potentials evoked by stimulation of other limbs they remained unchanged at these same points of the reticular formation or were reduced in amplitude while preserving the same temporal parameters. Cooling of the cortex thus selectively delays the development and reduces the amplitude of the response to stimulation of the limb in whose area of representation transformation of the afferent signal into a corticofugal volley is blocked. Consequently the normal development of both late and early components of the potential evoked in the reticular formation by somatic stimulation requires an additional volley, descending from the cortex, and formed as a result of transformation of the same afferent signal in the corresponding point of the somatosensory cortex.I. M. Sechenov Institute of Evolutionary Physiology and Biochemistry, Academy of Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol. 13, No. 1, pp. 32–38, January–February, 1981.     

Multicomponent synaptic potentials in rubrospinal neurons of cat brain evoked by corticofugal impulses

The compound nature of EPSP occurring in response to stimulation of the sensorimotor area of the cerebral cortex and the association area of the parietal cortex was shown during acute experiments on cats anesthetized by pentobarbital using an intracellular recording technique. The monosynaptic nature of the two first components of EPSP produced by corticofugal impulses spreading at the average rate of 18.5 and 7.5 msec, respectively, was established. It is postulated that these EPSP components are produced by activating the slow conducting pyramidal and corticorubral neurons. In a portion of rubrospinal neurons the first component of EPSP produced by corticofugal impulses was marked by a fast-rising phase and reflected electrophysiological activation of axosomatic synapses. Findings are discussed with regard to mechanisms reorganizing cortical synaptic inputs to the red nucleus neurons.L. A. Orbeli Institute of Physiology, Academy of Sciences of the Armenian SSR, Erevan. Translated from Neirofiziologiya, Vol. 17, No. 5, pp. 665–672, September–October, 1985.     

Effect of injury to the lateral reticular nucleus and nuclei of the inferior olive on electrical responses of the cerebellar cortex evoked by vagus nerve stimulation in cats

The role of the lateral reticular nucleus and nuclei of the inferior olive in the formation of cerebellar cortical evoked potentials in response to vagus nerve stimulation was determined in experiments on 28 cats anesthetized with chloralose and pentobarbital. After electrolytic destruction of the lateral reticular nucleus, in response to vagus nerve stimulation, especially ipsilateral, lengthening of the latent period and a decrease in amplitude of evoked potentials were observed; after bilateral destruction of this nucleus, evoked potentials could be completely suppressed. It is concluded that the lateral reticular nucleus relays interoceptive impulses in the vagus nerve system on to the cerebellar cortex. Additional evidence was given by the appearance of spike responses of Purkinje cells, in the form of mainly simple discharges, to stimulation of the vagus nerve. After destruction of the nuclei of the inferior olive, the latent period and the number of components of evoked potentials in response to vagus nerve stimulation remained unchanged but their amplitude was reduced. The role of the nuclei of the inferior olive as a regulator of the intensity of the flow of interoceptive impulses to the cerebellum is discussed.N. I. Pirogov Medical Institute, Vinnitsa. Translated from Neirofiziologiya, Vol. 9, No. 3, pp. 290–299, May–June, 1977.     

Activation of pontine and bulbar reticulo-spinal neurons in the cat by somatosensory stimuli of different modalities

The response pattern of reticulo-spinal (RS) neurons in two reticulo-spinal structures (n. reticularus pontis caudalis and n. reticularis gigantocellularis) to both electrical (somatic) nerve stimulation and natural mechanical innocuous (tapping with varying force) and noxious (pinch and prick) stimulation were investigated in chloralose-anesthetized cats. Bulbar and pontine neurons were found to vary considerably in their sensory characteristics: of the former 43% were activated only by high-threshold electrical nerve stimulation and noxious stimuli, while the remainder responded to innocuous stimuli as well. In the case of pontine neurons 81% produced a response to stimulation of low-threshold nerve fibers, and to innocuous as well as noxious stimuli. A relationship was found between the sensory characteristics of reticulo-spinal neurons and their axon conductance velocities. Various aspects and the likely functional significance of specialization in brainstem neurons of the pontine and bulbar reticular formation come under discussion.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 18, No. 4, pp. 461–469, July–August, 1986.     

Corticofugal regulation of auditory sensitivity in the bat inferior colliculus

Under free-field stimulation conditions, corticofugal regulation of auditory sensitivity of neurons in the central nucleus of the inferior colliculus of the big brown bat, Eptesicus fuscus, was studied by blocking activities of auditory cortical neurons with Lidocaine or by electrical stimulation in auditory cortical neuron recording sites. The corticocollicular pathway regulated the number of impulses, the auditory spatial response areas and the frequency-tuning curves of inferior colliculus neurons through facilitation or inhibition. Corticofugal regulation was most effective at low sound intensity and was dependent upon the time interval between acoustic and electrical stimuli. At optimal interstimulus intervals, inferior colliculus neurons had the smallest number of impulses and the longest response latency during corticofugal inhibition. The opposite effects were observed during corticofugal facilitation. Corticofugal inhibitory latency was longer than corticofugal facilitatory latency. Iontophoretic application of γ-aminobutyric acid and bicuculline to inferior colliculus recording sites produced effects similar to what were observed during corticofugal inhibition and facilitation. We suggest that corticofugal regulation of central auditory sensitivity can provide an animal with a mechanism to regulate acoustic signal processing in the ascending auditory pathway. Accepted: 15 July 1998     

Convergence and interaction of reticulofugal and peripheral afferent impulses on caudate neurons in the cat

Extracellular investigations on the activity of 269 caudate neurons during electrical stimulation of the midbrain reticular formation were carried out during chronic experiments on cats. Stimuli of different sensory modalities were used: auditory, mechanical, and visual. A response was observed to both reticular and peripheral stimulation in single neurons. The former produced an orthodromic response in 53% of caudate neurons, notable for its high probability of occurrence. A total of 23% of caudal neurons responded to this type of stimulation and application of stimuli of a single modality, while 14% responded polymodally. An excitatory response pattern prevailed during all types of stimulation. By applying twin stimuli to 100 caudate neurons, a capacity for interaction between reticular and acoustic inputs was discovered. Interaction was similarly observed in neurons which had reacted neither to separate application of both stimuli nor to either of the stimuli in isolation.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 19, No. 1, pp. 101–110, January–February, 1987.     

Role of cholinergic mechanisms in the genesis of some cortical responses

The dynamics of evoked potentials during blocking of cholinergic cortical structures was investigated in unanesthetized cats. Application of the anticholinergic drug benactyzine inhibits the negative phases of cortical responses to stimulation of the reticular formation and non-specific thalamic nuclei and also of responses to direct cortical stimulation. Direct cortical responses (DCRs), inverted by -aminobutyric acid, are also depressed, indicating the role of cholinergic mechanisms in the genesis of these responses. During blocking of cholinergic synapses, negative phases of the primary response (PR) and response to stimulation of the specific thalamic nucleus are facilitated. A tendency is then observed toward grouping of spontaneous unit discharges and abolition of inhibition of cortical neurons produced by high-frequency stimulation of the reticular formation. One cause of the increase in amplitude of the primary response (PR) to the action of anticholinergic drugs may be widening of the zone of cortical neurons involved in the response because of abolition of the localizing effect of inhibitory neurons.Institute of Physiology, Siberian Division, Academy of Sciences of the USSR, Novosibirsk. Translated from Neirofiziologiya, Vol. 2, No. 4, pp. 406–411, July–August, 1970.     

Reactions of neurons of the orbitofrontal cortex to stimulation of optic thalamic nuclei

The reactions of 288 neurons of the orbitofrontal cortex (OFC) to stimulation of the posteroventral (VP), ventral anterior (VA), and reticular (R) nuclei, as well as the median center (CM) of the thalamus, were investigated in acute experiments on cats. OFC neurons can be divided into four groups by their reactions to stimulation of thalamic nuclei: 1) those which respond with an increase in the frequency of the discharges to single and serial stimuli with a frequency of up to 20/sec; 2) those which respond doubtfully to single stimuli with a frequency of 4–12/sec; 3) those which respond with inhibition of the background impulses; 4) those which do not respond to stimulation of the nuclei. Stimulation of the thalamic nuclei evoked responses of OFC neurons with a large scatter of the latent period duration. The responses of neurons to stimulation of the VP (mean latent period 19.1±6.1 msec) had the shortest latent period (sometimes less than 3–4 msec). Reactions with a longer latent period developed upon stimulation of the VA (23.8±7.4 msec) and CM (42.8±12.8 msec). The uniqueness of the links of the OFC with the various optic thalamic nuclei is shown in an analysis of the material obtained and possible methods of the activation of the neurons of this region from thalamic structures are discussed.State Medical Institute, Kemerovo. Translated from Neirofiziologiya, Vol. 3, No. 4, pp. 350–358, July–August, 1971.     

Effects of bulbar stimulation on smooth muscle tone in the feline airway

Changes induced in tracheal smooth muscle tone by bulbar electrical stimulation were investigated in 30 cats anesthetized with a chloralose-urethane mixture and paralyzed with succinyl choline bromide. Raised tonus was mainly observed during stimulation of the caudal section of the dorsal motor nucleus of the vagus nerve, the vicinity of the nucleus ambiguus, and the adjoining reticular formation structures. Attenuation, however, was produced by stimulating bulbar reticular formation nuclei at a level 1 mm caudal and 6 mm rostral to the obex. Raised tonus is thought to be connected with activation of efferent neurons belonging to the motor nucleus of the vagal nerve, as well as axons of nucleus ambiguus neurons in transit through the medial zone, whilst attenuation is connected with excitation of sympathotonic reticular neurons, inhibitory neurons activated by pulmonary stretch receptors, and possibly with vagal efferent neurons activating the non-adrenergic inhibitory nervous system of the bronchi.Medical Institute, Latvian Ministry of Health, Riga. Cardiology Research Institute. Latvian Ministry of Health, Riga. Translated from Neirofiziologiya, Vol. 21, No. 3, pp. 320–326, May–June, 1989.     

Effects of stimulation of peripheral nerves,the lateral reticular nucleus,and the inferior olive on fastigial neurons of the cat cerebellum

Activity of fastigial neurons was investigated during stimulation of peripheral nerves of the fore- and hind limbs and also of brain-stem nuclei — the lateral reticular nucleus and inferior olive, transmitting indirect peripheral impulses to the cerebellum, in cats under superficial pentobarbital anesthesia. Stimulation of the nerves was accompanied by excitation of most neurons tested, reflected in repeated discharges to a single stimulus. Three main groups of responses latencies were distinguished: Those corresponding to conduction of peripheral impulses along slow and (partly) fast spinocerebellar tracts were predominant. Stimulation of the lateral reticular nucleus and inferior olive was accompanied by mono- and polysynaptic, and also by antidromic activation of fastigial neurons. Monosynaptic and antidromic activation of neurons are regarded as evidence of the presence of direct reticulo-and olivofastigial projections and of feedback in the system of these inputs into the nucleus fastigius respectively.L. A. Orbeli Institute of Physiology, Academy of Sciences of the Armenian SSR, Erevan. Translated from Neirofiziologiya, Vol. 13, No. 2, pp. 168–178, March–April, 1981.     

Unit responses of the thalamic and ventral anterior thalamic nuclei to electrical stimulation of thalamic relay nuclei in cats

Responses of 92 neurons of the reticular (R) and 105 neurons of the ventral anterior (VA) thalamic nuclei to stimulation of the ventrobasal complex (VB) and the lateral (GL) and medial (GM) geniculate bodies were investigated in cats immobilized with D-tobocurarine. Altogether 72.2% of R neurons and 76.2% of VA neurons responded to stimulation of VB whereas only 15.0% of R neurons and 27.1% of VA neurons responded to stimulation of GM and 10.2% of R neurons and 19.6% of VA neurons responded to stimulation of GL. The response of the R and VA neurons to stimulation of the relay nuclei as a rule was expressed as excitation. A primary inhibitory response was observed for only two R and three VA neurons. Two types of excitable neurons were distinguished: The first respond to afferent stimulation by a discharge consisting of 5–15 spikes with a frequency of 250–300/sec; the second respond by single action potentials. Neurons of the first type closely resemble inhibitory interneurons in the character of the response. Antidromic responses were recorded from 2.2% of R neurons and 7.8% of VA neurons during stimulation of the relay nuclei. Among the R and VA neurons there are some which respond to stimulation not only of one, but of two or even three relay nuclei. If stimulation of one relay nucleus is accompanied by a response of a R or VA neuron, preceding stimulation of another nucleus leads to inhibition of the response to the testing stimulus if the interval between conditioning and testing stimuli is less than 30–50 msec.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 8, No. 6, pp. 597–605, November–December, 1976.     

Reticular structures and reticulospinal pathways participating in the initiation and inhibition of spino-bulbo-spinal activity

Reflex discharges in intercostal nerves and activity of reticulospinal fibers of the ventral and lateral funiculi, evoked by stimulation of the reticular formation and of the splanchnic and intercostal nerves were investigated in cats anesthetized with chloralose (50 mg/kg). Brain-stem neuronal structures participating in the "relaying" of spino-bulbo-spinal activity were shown to lie both in the medial zones of the medullary and pontine reticular formation and in its more lateral regions; they include reticulospinal neurons and also neurons with no projection into the spinal cord. Structures whose stimulation led to prolonged (300–800 msec) inhibition of reflex spino-bulbo-spinal activity were widely represented in the brain stem, especially in the pons. Analogous inhibition of this activity was observed during conditioning stimulation of the nerves. Reticulospinal fibers of the ventral (conduction velocity 16–120 m/sec) and lateral (17–100 m/sec) funiculi were shown to be able to participate in the conduction of spino-bulbo-spinal activity to spinal neurons. In the first case fibers with conduction velocities of 40–120 m/sec were evidently most effective. Evidence was obtained that prolonged inhibition of this activity can take place at the supraspinal level.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Institute of Normal and Pathological Physiology, Slovak Academy of Sciences, Bratislava, Czechoslovakia. Translated from Neirofiziologiya, Vol. 8, No. 4, pp. 373–383, July–August, 1976.     

Neuronal activity of raphe nuclei of the brain stem in the cat

Evoked potentials were recorded in the system of raphe nuclei in experiments on unanesthetized, immobilized cats. Somatic stimulation proved to be the most effective of the different stimulations used (light flash, sound click, electrical stimulation of the skin of the limbs). Sound and light stimulation did not evoke pronounced responses, or the latter (to sound) were of a very low amplitude and irregular. In the second series of experiments on cats narcotized with nembutal (30–35 mg/kg) the spontaneous activity and activity evoked by somatic stimulation of single neurons of the caudal part of the raphe nuclei were studied. The overwhelming majority of neurons were characterized by spontaneous activity which changed (inhibited or facilitated) under the effects of somatic (especially repeated) stimulation; most of them reacted to stimulation of the skin of any limb. In the case of paired stimulation of the skin of limbs on different sides at large intervals (40–60 msec), inhibition of the test discharge occurred, whereas at small intervals summation (simple addition) of the impulses occurred. In their general characteristics the neurons of the raphe nuclei apparently differ little from the neurons of the reticular formation of the brain stem.Institute of Electrophysiology, Academy of Sciences of the Georgian SSR, Tbilisi. Translated from Neirofiziologiya, Vol. 3, No. 1, pp. 32–42, January–February, 1971.     

A mathematical model for the mechanism of rapid eye movements induced by an anticholinesterase in the decerebrate cat.

The oculomotor pattern which appears in intact preparations during desynchronized sleep is characterized by the irregular occurrence of isolated ocular movements and bursts of rapid eye movements (REM). This complex oculomotor pattern results from the activity of two premotor structures which influence the extraocular motoneurons during this phase of sleep: one is located in the pontine reticular formation, the other in the vestibular nuclei. In the decerebrate preparation the intravenous injection of an anticholinesterase leads to the appearance of a typical pattern of oculomotor activity, which differs from that occurring during physiological sleep in so far as it consists quite exclusively of bursts of REM which appear at very regular intervals. Lesion experiments as well as unit recordings have shown that these bursts of REM depend in particular upon rhythmic discharges of the vestibular nuclear neurons. The underlying anatomical structures responsible for these bursts of REM are therefore the vestibular nuclei, the oculomotor nuclei and the oculo-orbital system. This mechanism is under the influence of cholinergic reticular neurons which generate the oculomotor rhythm. We have postulated the existence of a self-excitatory cholinergic system, located in the pontine reticular formation, whose steady discharge impinges upon an oscillatory neuronal system located in the dorso-lateral pontine tegmentum, which transforms the tonic input into a sinusoidal final output. We have assumed also that the periodic increases in the discharge frequency of this oscillatory system trigger a fast phase generator acting on the different components of the REM system, and that the behavior of each component follows a first-order differential equation. The state of excitation of the components of the system is defined as proportional to frequency of nerve impulses. Assuming ipsilateral and crossed connections, a pattern of oculomotor activity is obtained that simulates the experimental oculomotor output fairly well. The repetition of the eye jerks is described by a Fourier series. The model proposed in this paper may be taken as a first approach in describing the generation mechanism of REM, and as a theoretical guide to new experimental researches and the development of other more realistic models.     

Single unit responses of the reticular and ventral anterior nuclei of the thalamus to electrical stimulation of the centrum medianum

In acute experiments on cats anesthetized with thiopental (30–40 mg/kg, intraperitoneally) and immobilized with D-tubocurarine (1 mg/kg) responses of 145 neurons of the reticular and 158 neurons of the ventral anterior nuclei of the thalamus to electrical stimulation of the centrum medianum were investigated. An antidromic action potential appeared after a latent period of 0.3–2.0 msec in 4.1% of cells of the reticular nucleus and 4.4% of neurons of the ventral anterior nucleus tested in response to stimulation. The conduction velocity of antidromic excitation along axons of these neurons was 1.7–7.6 m/sec. Neurons responding with an antidromic action potential to stimulation both of the centrum medianum and of other formations were discovered, electrophysiological evidence of the ramification of such an axon. Altogether 53.8% of neurons of the reticular nucleus and 46.9% of neurons of the ventral anterior nucleus responded to stimulation of the centrum medianum by orthodromic excitation. Among neurons excited orthodromically two groups of cells were distinguished: The first group generated a discharge consisting of 6–12 action potentials with a frequency of 130–640 Hz (the duration of discharge did not exceed 60 msec), whereas the second responded with a single action potential. Inhibitory responses were observed in only 0.7% of neurons of the reticular nucleus and 4.4% of the ventral anterior nucleus tested. Afferent influences from the relay nuclei of the thalamus, lateral posterior nucleus, and motor cortex were shown to converge on neurons responding to stimulation of the centrum medianum.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 12, No. 1, pp. 36–45, January–February, 1980.     

Effects of substantia nigra stimulation on high- and low-threshold response in reticular neurons

The effects of electrical stimulation of the substantia nigra (NS) pars compacta on somatosensory response in pontine neurons (from n. reticularis pontis caudalis) and reticular cells (n. reticularis gigantocellularis) were investigated in chloralosed cats. These effects were found to be inhibitory and tended mainly towards high-threshold activation of reticular neurons: responses induced by activation of high-threshold somatic efferents were those mainly inhibited in 71% of test cells. Inhibition of low-threshold response induced by tactile stimuli emerged less clearly or not at all. Potential mechanisms and the functional significance of these SN influences on reticular neurons are discussed.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 21, No. 6, pp. 772–780, November–December.