Electrophysiological investigation of the cat ciliary ganglion

Electrical responses of some nerves of the ciliary ganglion to stimulation of its other nerves were recorded, and intracellular recordings were also made from neurons of the ganglion (in situ). The overwhelming majority of preganglionic fibers terminate synaptically on neurons of the ganglion. Postganglionic fibers leave in the lateral and medial ciliary nerves, in which the velocity of conduction of excitation ranges from 1.9 to 9.0 m/sec. A few preganglionic fibers pass through the ciliary ganglion into the lateral ciliary nerve, giving off collaterals to neurons of the ganglion, so that stimulation of the lateral ciliary nerve evokes a response in the medial ciliary nerve (preganglionic axon reflex). The resting potential of neurons of the ciliary ganglion is 57±2.8 mV, and their action potential 68±3.6 mV. Single orthodromic stimulation usually evokes a single action potential in a neuron. The amplitude of the EPSP is increased during hyperpolarization of the postsynaptic membrane, confirming the chemical nature of synaptic transmission in the ganglion. The antidromic response consists of an IS-component and spike. The spike is followed by after-hyperpolarization, with a mean amplitude equal to 31% of the spike amplitude, and the time taken for it to fall to one–third of its initial amplitude is 75–135 msec.A. A. Bogomolets' Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 1, No. 1, pp. 101–108, July–August, 1969.     

Effects of stimulating the central gray matter on neuronal response in the cat medial thalamic nuclei

This study was performed on the effects of stimulating the midbrain central gray matter (CGM) on neuronal response in the association medial thalamic nuclei evoked by stimulation of A-alpha and A-delta fibers of the infraorbital nerve and the caudal nucleus of the spinal trigeminal tract (CN STT) and tooth pulp stimulation using cats anesthetized by thiopental-chloralose as experimental animals. Stimulating the CGB with trains of stimuli was found to evoke an excitatory response in a percentage of the neurons tested, in which latency fluctuated between 15 and 40 msec. Applying conditioned stimuli to the CGM caused suppression of response to afferent impulses in neurons belonging to the "convergent" and "low" and "high" threshold groups. Responses induced by stimulating tooth pulp and A-delta fibers showed 100% inhibition as compared with 86% during A-alpha fiber and infraorbital nerve stimulation. The fact that stimulating the CGM produces an inhibitory effect on the response of thalamic neurons evoked by stimulation of both peripheral afferents and the CN STT would indicate that the CGM can exert a direct action on thalamic neuronal activity.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 19, No. 5, pp. 660–665, September–October, 1987.     

Suppression of postsynaptic response in trigeminal motoneurons by stimulating the midbrain central gray matter

The effects of stimulating the midbrain central gray matter (CGM) on motoneuronal response in trigeminal nerves were investigated in anesthetized cat. It was found that stimulating the CGM did not induce postsynaptic response in these motoneurones. Conditioning stimulation of the CGM brought about suppression of motoneuronal postsynaptic response to stimulation of tooth pulp and high threshold infraorbital nerve afferents without affecting motoneuronal antidromic response and jaw-opening reflex as induced by stimulating the caudal nucleus of the spinal trigeminal tract. It was thus concluded that stimulating the CGM exerts no direct effect on motoneurons but does have an influence on postsynaptic response — a result of modulation of the afferent spike flow at interneuronal level.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 22, No. 4, pp. 543–549, July–August, 1990.     

Some characteristics of the afferent flow during noxious stimulation of the skin

Quantitative characteristics of the afferent impulse flow in a cat cutaneous nerve during stimulation of the skin with acid, needles, and pins were studied by a cross-correlation method. The appearance of a nociceptive response served as the test of noxious stimulation. Mechanical and chemical noxious stimuli, acting directly on the nerve fiber, activate the same peripheral channels as weak tactile stimuli exciting receptors. Spike trains under these circumstances differed in the absolute and relative numbers of active A and C fibers and the duration of activity in them. The nociceptive response is brought about through marked predominance of activity in C fibers compared with A fibers and through its long duration in both types of fibers but, in particular, in C fibers. An optical correlometer can be used to investigate activity of a whole nerve.Research Institute of Applied Mathematics and Cybernetics, N. I. Lobachevskii Gor'kii State University. Translated from Neirofiziologiya, Vol. 8, No. 2, pp. 168–176, March–April, 1976.     

Influence of picrotoxin and duration of conditioning on the induction of associative long-term potentiation in the mouse hippocampal area CAl in vitro

Field potentials (FP) induced in the radial layer of area CAl by stimulating Schaffer's collaterals (C2) were recorded in murine hippocampal slices and associative long-term potentiation (ALP) produced by combined tetanization of C2 and another group of fibers (C1) was investigated. The effects of simultaneous (C1 and C2) and successive activation (with C1 preceding C2 by 200 msec) of the two inputs were compared. Tetanization preceded by activation of C1 ("conditioning" input) was more effective in experiments with short (30 msec, 100 Hz) trains of stimuli. Tetanization with simultaneous activation of the two inputs as well as tetanization of C1 input by prolonged (150 msec) spike trains with inhibition were blocked by 5·10^–6 M picrotoxin. It is suggested that ALP induced by short trains of stimuli succeeding at 200 msec intervals serves as a more suitable model of memory than that induced by prolonged trains (of 1 sec).Brain Research Institute, National Mental Health Research Center, Academy of Sciences of the USSR, Moscow. Institute of Chemical Physics, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 22, No. 2, pp. 215–223, March–April, 1990.     

Electrophysiological investigation of the conduction of excitation in the pterygopalatine ganglion of the cat

When responses in some nerves of the pterygopalatine ganglion of the cat in situ to stimulation of its other nerves were recorded it was found that most fibers passing through the ganglion are continuous sympathetic postganglionic fibers (at least three groups). Most of the parasympathetic preganglionic fibers forming synapses on neurons of the ganglion constitute a group of fibers with the same threshold of excitation. Intracellular recording from single neurons of the pterygopalatine ganglion showed that stimulation of the Vidian nerve evokes orthodromic spike potentials in some neurons of the ganglion with a short latent period, and in others with a long latent period (2.5–6.0 and 10–44 msec, respectively). Evidently only fast-conducting fibers terminate synaptically on most neurons of the ganglion and only slow-conducting fibers on some of them. Recording from intact nerves of the pterygopalatine ganglion revealed no tonic activity in them. Microelectrode recording from single neurons of the ganglion showed that either the frequency of generation of spike potentials is relatively low (1–3/sec) or such potentials are absent altogether.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 8, No. 5, pp. 514–520, September–October, 1976.     

Effects of stimulating midbrain central gray matter on neuronal response in the caudal trigeminal nucleus to peripheral nerve stimulation

Stimulating the midbrain central gray matter (CGM) with trains of 10–20 stimuli was found to inhibit response to electrical stimulation of infraorbital nerve and tooth pulp A-alpha and A-delta afferents at 100 msec intervals in 65% of the caudal trigeminal nucleus in neurons tested during experiments on cats under chloralose-Nembutal anesthesia. Response was inhibited most effectively in convergent neurons (activated by stimulating infraorbital nerve and tooth pulp A-alpha and A-delta afferents) to stimulating tooth pulp (0.76) and, to a somewhat lesser degree, to stimulation of A-alpha afferents (0.6). For high-threshold neurons (activated by stimulating infraorbital nerve and tooth pulp A-delta afferents), success rate of inhibiting response under the effects of CGM stimulating measured 0.71 and 0.48 for low-threshold cells (activated by stimulating infraorbital nerve A-alpha afferents). Stimulating CGM produced an excitatory response in 10 caudal trigeminal nucleus neurons within 7.5–20 msec; after this neurons showed no reaction to peripheral nerve stimulation for a 200–450 msec period. The possible involvement of these neurons in pressing the mouth-opening reflex produced by CGM stimulation is discussed in this article.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 20, No. 6, pp. 729–736, November-December, 1988.     

Effects of stimulating the midbrain central gray matter on neuronal response in the cat ventroposteromedial thalamic nucleus

The effects of stimulating the midbrain central gray matter (CGM) on neuronal response in the ventroposteromedial (VPM) nucleus produced by stimulating tooth pulp, A-alpha and A-delta fibers of the intraorbital nerve and the caudal nucleus of the spinal trigeminal tract (CN STT) were investigated during experiments on cats under thiopental-chloralose anesthesia. It was found that applying trains of stimuli to the CGM produced excitatory responses in a proportion of the test neurons with latencies of up to 30 msec. Application of conditioning stimulus to the CGM led to suppression of response of efferent stimulation in neurons belonging to low-threshold, convergent, and high-threshold groups. Responses produced in 40% of neurons by stimulating tooth pulp and A-delta fibers of the suborbital nerve, as well as those evoked in 26.4% of thalamic VPM cells by stimulating A-alpha fibers of the suborbital nerve were completely suppressed. The inhibitory effect found when stimulating CGM on response in certain neurons, produced by stimulating both the peripheral nerve and the CN STT, would indicate that the CGM could exert an influence on the activity of thalamic VPM neurons directly.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 20, No. 5, pp. 688–694, September–October, 1988.     

Functional properties of lamprey electroreceptors

Spike discharges in nerve fibers, evoked by stimulation of electroreceptors by an electric field directed along the body axis (square pulses of current and a sinusoidal current) were recorded in the lampreyLamperta fluviatilis (L.). Excitation of electroreceptors was shown to arise through the action of the cathode. Minimal values of electric field at which appreciable changes took place in spike activity were 10–60 µV/cm for different nerve fibers. The optimal frequency range of sinusoidal electrical stimulation was 0.05–0.5 Hz. It is suggested that electroreceptors of the Agnatha (caudata) and of gnathostomatous cartilaginous fish share a common origin.Murmansk Marine Biological Institute, Kola Branch, Academy of Sciences of the USSR, Dal'nie Zelentsy, Murmansk Region. Translated from Neirofizioloigya, Vol. 16, No. 1, pp. 105–110, January–February, 1984.     

Afferent activity in thin myelinated and unmyelinated cutaneous nerve fibers during mechanical stimulation of skin receptors

Afferent activity in thin myelinated and unmyelinated cutaneous nerve fibers was analyzed by an impulse collision method and by methods improving the signal-to-noise ratio in the record of the antidromic action potential. The following groups were distinguished among the thin myelinated and unmyelinated nerve fibers on the basis of the results of investigation of conduction velocities, thresholds of electrical excitation, and response to mechanical stimulation: A ₁ (conduction velocity 30-14 m/sec) — a relatively larger number of these fibers conducts excitation in response to weak mechanical stimulation; A ₂ (14–4.0 m/sec) — the receptors of these fibers are more easily excited by a strong stimulus; a group of "mixed" fibers, containing myelinated and unmyelinated nerve fibers (4–2 m/sec), conducting excitation in response to both types of mechanical stimulation; C₁ (2.0–1.0 m/sec) — a fairly large number of these unmyelinated fibers conducts impulses in response to weak mechanical stimulation; C₂ (1.0–0.15 m/sec) the majority of fibers of this group is connected with receptors requiring strong mechanical stimulation for their excitation.Research Institute of Applied Mathematics and Cybernetics, N. I. Lobachevskii State University, Gor'kii. Translated from Neirofiziologiya, Vol. 8, No. 1, pp. 67–75, January–February, 1976.     

Decrease in excitability of LG following habituation of the crayfish escape reaction

Crayfish escapes from threatening stimuli to the abdomen by tailflipping upwards and forwards. This lateral giant (LG)-mediated escape reaction habituates readily upon repetitive sensory stimulation. Using an isolated abdominal nerve cord preparation, we have analyzed the change in LG activity by applying additional sensory stimulation after different periods following habituation to characterize the retention of LG habituation. Results show that the LG mediated response habituates more quickly, but the retention time is shorter, as repetitive sensory stimulation is applied at progressively shorter inter-stimulus time intervals. The spike response of LG recovers quickly, within several minutes after habituation, but they fail to spike when an additional stimulus is applied after specific long periods following habituation. The critical period of the delay for this decrease in excitability of LG is dependent on the inter-stimulus time interval of the initial repetitive stimulus. As the inter-stimulus interval became longer, the delay needed for decrease in excitability became shorter. Furthermore, the local injection of 10^–6 mol l^–1 octopamine into the neuropil just following habituation promotes the achievement of decrease in excitability. No effects were observed when 10^–6 mol l^–1 serotonin and tyramine were injected. These results suggested octopamine promotes decrease in excitability of LG following habituation.     

Responses of cerebellar Purkinje cells to mechanical stimulation of the Achilles' tendon

Responses of cerebellar Purkinje cells to mechanical stimulation of the Achilles' tendon were studied in unanesthetized decerebrate cats. Approximately two-thirds of the Purkinje cells tested were activated in response to stimulation through climbing fibers, i.e., they generated a complex spike. In half of these cells (group A) the probability of appearance of a complex spike to a blow on the tendon was from 0.5 to 0.9 and the latent period of response from 20 to 25 msec. Purkinje cells with a latent period of response of over 35 msec were characterized by low probability of response (under 0.5) to a tap (group B). Responses of Purkinje cells to excitation of mossy fibers were weaker and more varied.I. M. Sechenov Institute of Evolutionary Physiology and Biochemistry, Academy of Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol. 13, No. 2, pp. 159–167, March–April, 1981.     

Role of different types of fibers of the infraorbital nerve in synaptic activation of masseter and digastric motoneurons

Postsynaptic potentials of motoneurons of the masseter and digastric muscles evoked by stimulation of the infraorbital nerve with a strength of between 1 and 10 thresholds were investigated in cats anesthetized with a mixture of chloralose and pentobarbital. Depending on their ability to be activated by low-threshold afferents of this nerve, motoneurons of the masseter were divided into two groups. Stimuli with a strength of 1.2–2.5 times above threshold for the most excitable fibers of the infraorbital nerve evoked short-latency EPSPs in the motoneurons of the first group; a further increase in stimulus strength (3–9 thresholds) led to the appearance of IPSPs with latent periods of 2.8–3.5 msec. Motoneurons of the second group responded to stimulation of the infraorbital nerve with a strength of 3–9 thresholds by IPSPs whose latent periods varied from 6 to 8 msec. Stimuli below 3 thresholds in strength evoked no responses in these motoneurons. Stimulation of the infraorbital nerve with pulses of between 1 and 2 thresholds in strength evoked EPSPs in digastric motoneurons, but an increase in the strength of stimulation led to action potential generation. The presence of many excitatory and inhibitory inputs formed by afferent fibers of different types evidently provides a basis for functional diversity of jaw-opening and jaw-closing reflexes.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 12, No. 6, pp. 596–603, November–December, 1980.     

Excitation of cat spinal cord dorsal column fibers during stimulation of different fiber groups of cutaneous and somatic nerves

The effects of electrically stimulating different groups of nerve fibers supplying the skin and muscle on evoked potentials in cat spinal cord dorsal columns were studied. Significant differences in the configuration of dorsal column potentials recorded in response to stimulation of these nerves were found. It was shown that cutaneous nerve unmyelinated fibres were connected to unmyelinated dorsal column fibers. In addition, excitation of cutaneous C-fibers lead to activation of dorsal column fibers with the maximum conduction velocity. The somatic nerve was only connected to myelinated dorsal column fibers, and excitation of its non-myelinated fibers did not cause other types of dorsal column fibers to be activated. It is suggested that the acceleration of cutaneous signal transmission in the dorsal column system may be brought about by the necessity for rapid warning of potentially harmful stimuli.Medical Institute, Russian Federation Ministry of Public Health, Nizhny Novgorod. Translated from Neirofiziologiya, Vol. 24, No. 5, pp. 625–635, September–October, 1992.     

Response of cat auditory cortex neurons to tonal stimulation during and after nembutal anesthesia

During acute experiments on 20 cats a comparative study was made of neuronal reaction to a tone, as recorded during the first few hours after administration of Nembutal and after an interval of 10–30 h. No spontaneous activity was seen in 89% of auditory cortex neurons of the anesthetized cats; these produced a sterotyped on- response to the optimal frequency tone. Late neuronal spike discharges at distinct intervals of 100–150 msec appeared in response to the setting up of acoustic stimulation after a brief latent reaction lasting 9–15 msec. It was shown that this stimulation did not produce an off-response in the cortical neurons. When the animals emerged from Nembutal anesthesia, the neurons reacted very differently to the optimal frequency tone. About 76% of the cells produced an on, on-off or off response, while about 21% responded with either tonic spike discharges or total inhibition of these throughout the acoustic stimulation. In unanesthetized cats the vast majority of AI cortical neurons were capable of reacting as long as the stimulus lasted. It is shown how this ability is lost under deep Nembutal anesthetic.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 17, No. 6, pp. 728–737, November–December, 1985.     

Responses of neurons of the frog nucleus isthmi to optic nerve stimulation

Responses of single units in the region of the nucleus isthmi were investigated in frogs immobilized with diplacin by means of extracellular capillary liquid microelectrodes. The neurons of this region were not spontaneously active and, after electrical stimulation of the contralateral optic nerve with a single pulse, they gave a single spike discharge with a minimal latent period of 20–110 msec. On increasing the strength of stimulation from threshold to maximal these latent periods were significantly reduced, indicating marked development of summation processes in the corresponding neuronal pathway. Only 14% of the neurons (7 of 57) discharged in response to stimuli exciting myelinated but not exciting unmyelinated optic fibers. All neurons were characterized by instability of the latent period of the evoked discharge; consequently, they were not excited antidromically. The possible functional role of the nucleus isthmi region in the Anura is discussed.A. N. Severtsov Institute of Evolutionary Morphology and Ecology of Animals, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 9, No. 1, pp. 33–40, January–February, 1977.     

Investigation of the mechanism of temperature sensitivity of the electroreceptors of ampullae of lorenzini

In experiments on Black Sea skates (Raja clavata), the potential of the receptor epithelium of the ampullae of Lorenzini and spike activity of single nerve fibers connected to them were investigated during electrical and temperature stimulation. Usually the potential within the canal was between 0 and –2 mV, and the input resistance of the ampulla 250–400 k. Heating of the region of the receptor epithelium was accompanied by a negative wave of potential, an increase in input resistance, and inhibition of spike activity. With worsening of the animal's condition the transepithelial potential became positive (up to +10 mV) but the input resistance of the ampulla during stimulation with a positive current was nonlinear in some cases: a regenerative spike of positive polarity appeared in the channel. During heating, the spike response was sometimes reversed in sign. It is suggested that fluctuations of the transepithelial potential and spike responses to temperature stimulation reflect changes in the potential difference on the basal membrane of the receptor cells, which is described by a relationship of the Nernst's or Goldman's equation type.I. P. Pavlov Institute of Physiology, Academy of Sciences of the USSR, Leningrad. I. M. Sechenov, Institute of Evolutionary Physiology and Biochemistry, Academy of Sciences of the USSR, Leningrad. Pacific Institute of Oceanology, Far Eastern Scientific Center, Academy of Sciences of the USSR, Vladivostok. Translated from Neirofiziologiya, Vol. 12, No. 1, pp. 67–74, January–February, 1980.     

Analysis of evoked discharges in hypothalamic neurons to somatosensory,acoustic, and photic stimulation

Single unit activity in the supramammillary, mammillary, and anterior hypothalamic areas in response to acoustic, photic, and sciatic nerve stimulation was recorded in cats anesthetized with chloralose and immobilized with succinylcholine. In response to sensory stimulation the spontaneous firing rate was increased or decreased, and silent neurons were activated. Evoked potentials of the silent neurons had the shortest latent period to acoustic and somatosensory stimulation (15 msec), and rather longer to photic stimulation (30 msec); in some cases their latent period was 200 msec. Histograms of interspike interval distribution showed a maximum for intervals of up to 50 msec. Histograms of spike distribution relative to the beginning of stimulation showed maximal density between 100 and 200 msec. A high degree of convergence of excitation was found on units of the anterior as well as the posterior hypothalamus. Unit responses in the hypothalamus to sensory stimuli of all three modalities are regarded as being of secondary, nonspecific type.L. A. Orbeli Institute of Physiology, Academy of Sciences of the Armenian SSR, Erevan. Translated from Neirofiziologiya, Vol. 3, No. 6, pp. 592–598, November–December, 1971.     

Responses of units in the magnocellular part of the medial geniculate body to acoustic and somatosensory stimulation

Responses of 150 neurons in the magnocellular part of the medial geniculate body to clicks and to electrodermal stimulation of the contralateral forelimb were investigated in cats immobilized with myorelaxin. Of the total number of neurons 65% were bimodal, 16.6% responded only to clicks, and 15.4% only to electrodermal stimulation. The unitary responses were excitatory (spike potentials) and inhibitory (inhibition of spontaneous activity). Responses beginning with excitation occurred more frequently to stimulation by clicks than to electrodermal stimulation, whereas initial inhibition occurred more often to electrodermal stimulation. The latent period of the initial spike potentials in response to clicks and to electrodermal stimulation was 5–27 and 6–33 (mean 11.6 and 16.2) msec respectively. Positive correlation was found between the latent periods of spike potentials recorded in the same neurons in response to clicks and to electrodermal stimulation, and also to electrodermal stimulation and to stimulation of the dorsal funiculus of the spinal cord. It is concluded that the magnocellular division of the medial genicculate body is a transitional structure between the posterior ventral nucleus and the parvocellular division of the medial geniculate body, and that in addition, it is connected more closely with the auditory than with the somatosensory system. It is suggested that the somatosensory input into the magnocellular division of the medial geniculate body is formed mainly by fibers of the medial lemniscus.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 10, No. 2, pp. 133–141, March–April, 1978.     

Efferent activity in the phrenic nerve during startle reflex in chloralose anesthetized cats

Efferent activity was investigated in the phrenic nerve during startle reflex manifesting as somatic nerve discharges (lower intercostal nerves and the nerve endings) in chloralose anesthetized cats. Inhibition (usually of short duration, lasting 23–36 msec) of inspiration activity was found to be the main component of response in the phrenic nerve in the shaping of "low threshold" startle reflex produced by acoustic and tactile stimuli and stimulation of low threshold peripheral afferents. Reflex discharge prevailed amongst the response patterns produced in the phrenic nerve by stimulating high threshold afferents, i.e., early (propriospinal) and late (suprasegmental, arising from stimulating intercostal nerve) or late only (when stimulating the hindlimb nerves). Two patterns of late response could be distinguished, one on inspiration (found in roughly 3 out of 4 experiments) and other on exhalation — the respiratory homologs of somatic startle reflex. Response pattern is described throughout the respiratory cycle. Structure and respiratory modulation of reflex responses produced in the phrenic nerve by stimulating bulbar respiratory structure are also examined. Possible neurophysiological mechanisms underlying phrenic response during the shaping of startle reflex are discussed.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 19, No. 4, pp. 473–482, July–August, 1987.