PubMed Health⌕ Search

Biomedical subjects

Iu P Limanskiĭ

Publications and source records attributed to Iu P Limanskiĭ.

At least 19 recordsLinked to original sources
PubMed1992

[Changes in background activity of periaqueductal gray neurons through application of serotonin or inhibition of its synthesis].

Application of serotonin (ST, 1.10(-4) M to periaqueductal grey neurons influenced background activity (BA) only in the third group of cells. In 45.5% of them ST evoked depression of BA. Through application of ST remarkable potentiation of BA inhibition evoked by locus coeruleus (LC), substantia nigra (SN) stimulation was found, but inhibitory affects of nucleus raphe magnus (NRM) were less intensive. After intraperitoneal injection of p-chlorophenylalanine the efficiency of NRM stimulation became lower, but influences of LC and SN on BA increased. The mechanisms of serotoninergic effects on BA of periaqueductal grey neurons are discussed.

Animals↗
PubMed1992

[Modulation of periaqueductal gray neuronal activity by influences of brain stem monoaminergic structures].

Studies of spontaneous firing (SF) in the midbrain periaqueductal gray (PAG) neurons before and after stimulation of nucleus raphe magnus, locus coeruleus and substantia nigra were performed on the rat anesthetized with Hexenal (200 mg/kg). Three types of neurons different in SF structure were found. Stimulation of indicated structures increased SF rate in 11-14.5% and decreased 31-47% of the studied neurons of the third group. Simultaneous stimulation of two structures did not induce a remarkable increase of SF rate. If one of two simultaneously stimulated structures suppressed SF the ultimate effect was, as a rule, depression of SF. Greatest suppression of SF was observed if stimulation of nucleus raphe magnus was induced. Role of PAG in organization of the brain stem component of antinociceptive mechanism is discussed.

Animals↗
PubMed1989

[Role of the serotoninergic system in inhibiting the jaw-opening reflex induced by stimulation of the central gray matter of the midbrain].

Effect exerted by stimulation of the central grey matter (CGM) of the midbrain and nucleus raphe dorsalis (nRD) by a short train of stimuli (20) followed with the rate of 400/s on the high-threshold jaw-opening reflex (HJOR) evoked by electrical irritation of the tooth pulp was studied during serotonin synthesis blockade after parachlorphenylalanine (pCPA) administration (300 mg/kg intraperitoneally) in awake cats. It was found that the inhibitory effect of the CGM and nRD stimulation on HJOR decreased 24 hours after the pCPA injection. Inhibition of HJOR induced by CGM and nRD stimulation became minimal 96 hours after the pCPA administration: reflex magnitude decreased only by 33% and duration of inhibition was 200-250 ms. Conclusion is made about serotonin participation in HJOR depression induced by CGM and nRD stimulation. The possible participation of other neuromodulators in such inhibition is discussed.

Animals↗
PubMed1989

[The effect of stimulation of the substantia nigra on low- and high-threshold startle reflexes in the cat].

Effects of the substantia nigra (pars compacta) stimulation on two functional types of startle reflexes were studied in chloralose-anesthetized cats. The reflexes were the low-threshold ones evoked by tactile stimuli (T-reflex) and high-threshold ones evoked by intense peripheral nerve stimulation (spino-bulbo-spinal, SBS reflex). It was found that substantia nigra stimulation exerted mainly inhibitory influences on both types of reflexes. However the depression of the SBS-reflex was always more profound and long lasting (up to 8 min) than that of T-reflex. The latter reflex was sometimes facilitated.

Animals↗
PubMed1989

[The effect of stimulation of the substantia nigra on the low- and high-threshold neuronal responses of the reticular formation].

Modulation of somatosensory responses of bulbar (n. reticularis gigantocellularis) and pontine (n. reticularis pontis caudalis) reticular neurons by the substantia nigra (SN) stimulation was studied in cats under light chloralose anesthesia. It was found that the action of the SN stimulation on the somatosensory activity of the neurons was based on the principle of the inhibitory control of their high-threshold synaptic somatosensory inputs; high-threshold neuronal responses were much more depressed than the low-threshold ones in most (71%) of the studied reticular units. Possible neuromodulatory mechanisms and functional significance of described influences are discussed.

Animals↗
PubMed1989

[Influence of stimulation of the central gray matter on low- and high-threshold startle reflexes].

Influences of the periaqueductal gray matter (PAG) stimulation on high-threshold jaw opening reflex (JOR) evoked by tooth pulp stimulation and on two functional types of startle reflexes were studied in chloralose anesthetized cats; the startle reflexes were high-threshold ones evoked by intense peripheral nerve stimulation (spino-bulbo-spinal, SBS, reflex) and low-threshold ones evoked by tactile stimuli (tactile spino-reticulo-spinal, TSRS, reflex). Stimulation of the majority of PAG sites induced considerable inhibition of JOR as well as profound depression of SBS-reflexes and moderate depression of TSRS-reflexes. Some PAG sites were found to exert a facilitatory action on the latter reflex. Effects of PAG stimulation were short-term (hundred ms) and/or long-lasting (minutes). Possible mechanisms of these effects are discussed.

Animals↗
PubMed1988

[Effect of the stimulation of the central gray substance of the midbrain on the neuronal responses of the trigeminal caudal nucleus during peripheral excitations].

Experiment on cats under chloralose-nembutal anaesthesia has shown that 65% responses of caudal trigeminal nucleus neurons to the activation of the tooth pulp, A alpha and/or A delta infraorbital nerve afferents were completely suppressed by conditioning stimulation of the central grey matter (CGM) by a train of stimuli (10-20) that followed with the rate of 200-400/s, if the interval between conditioning and testing stimuli did not exceed 100 ms. Conditioning stimulation of the CGM inhibited responses of the "convergent" neurons to the activation of tooth pulp most efficiently (0.76) and those to the activation of A alpha afferents more weakly (0.6). Effectiveness of "high-threshold" neurons inhibition under the effect of CGM stimulation was 0.71 and that of "low-threshold" neurons--0.48. Ten caudal trigeminal nucleus neurons were activated by the CGM stimulation with the latency of 7.5-20 ms. These neurons did not respond to peripheral nerve stimulation for 200-450 ms after CGM activation. A possible role of caudal trigeminal nucleus neurons in the CGM inhibition of jaw opening reflexes is discussed.

Action Potentials↗
PubMed1988

[Effect of stimulation of the central gray substance on the low- and high-threshold responses of the reticular neurons in the pons and medulla oblongata].

The modulation of somatosensory responses of bulbar (n. reticularis gigantocellularis) and pontine (n. reticularis pontis caudalis) reticular neurons by electrical stimulation of periaqueductal gray matter (PGM) was studied in cats under light chloralose anaesthesia. PGM points which evoked the inhibition of nociceptive jaw opening reflex were stimulated. It was found that in most cases (88%) the PGM stimulation had an inhibitory effect on both nociceptive and non-nociceptive responses of reticular neurons. For bulbar cells with predominant high-threshold inputs nociceptive responses were depressed much stronger than non-nociceptive ones and in pontine neurons for which low-threshold inputs were predominant non-nociceptive responses were inhibited mainly. The data suggest that the inhibitory action of PGM stimulation on somatosensory activity of reticular neurons are based on the principle of the "control of their main synaptic input".

Animals↗
PubMed1986

[Effect of stimulation of the superior colliculi of the tectum mesencephali on the motor neurons of the neck muscles of the cat].

Postsynaptic potentials evoked by stimulation of three points of the superior colliculus in motoneurons of neck muscles were studied in experiments on cats under chloralosenembutal anesthesia. Stimulation of ipsilateral superior colliculus evoked EPSP with latencies ranging from 1.5 to 3.5 ms in 49 motoneurons. Stimulation of contralateral superior colliculus evoked EPSP with latencies ranging from 1.5 to 3.0 ms in 63 motoneurons and IPSP with latencies ranging from 2.6 to 5.0 ms in 10 motoneurons. It is suggested that the recorded postsynaptic potentials are mono- and disynaptic.

Animals↗
PubMed1986

[Features of activation of reticulospinal neurons of the pons and medulla oblongata of the cat by somatosensory stimuli of different modalities].

Response of reticulo-spinal (RS) neurons in two reticular structures (n. reticularis pontis caudalis and n. reticularis gigantocellularis) to electrical nerve stimulation and natural mechanical non-nociceptive (tapping) and nociceptive (pinch and prick) stimuli were studied in chloralose-anesthetized cats. Essential differences in sensory properties of the pontine and bulbar RS-neurons were found. About a half of bulbar RS-neurons (43%) were activated only by high-threshold somatic afferents and nociceptive stimuli, the rest--by both nociceptive and non-nociceptive ones. On the contrary the most of pontine neurons (81%) responded either to non-nociceptive or to both noci- and non-nociceptive stimuli. A clear-cut correlation between sensory characteristics of the RS-neurons and their axon conduction velocities was established. Data obtained evidence for the existence of some spatial (rostro-caudal) differentiation of brainstem RS-neurons with different functional properties. Peculiarities of this differentiation and its possible functional significance are discussed.

Animals↗
PubMed1984

[Inhibition of mouth-opening reflexes in the cat by stimulation of the central gray and raphe nuclei].

Effect of stimulation of midbrain central grey (CG) and raphe nuclei (RN) on jaw opening reflexes evoked by excitation of high-threshold (tooth pulp) and low-threshold (A-alpha infraorbital nerve fibres) afferents was studied in cats under chloralose-nembutal anesthesia. High-threshold jaw opening reflex (HJR) was effectively suppressed after conditioning stimulation of CG and RN. Law-threshold jaw opening reflex (LJR) also was suppressed, but less deeply than HJR during stimulation of RN and caudal part of CG, but it was not changed during stimulation of rostral CG. Duration of inhibition of HJR and LJR depended on parameters of CG and RN stimulation. Short trains (10-20) of stimuli (200-400/s) evoked the inhibition with latency 20-25 ms. Depression of HJR in the 40-150 ms range reched 100%, depression of LJR-30-50%. Depression of HJR lasted for 1000 ms, that of LJR-500 ms. Prolonged rhythmic stimulation of CG and RN (50/s during 30 s) evoked inhibition of HJR and LJR that lasted up to 60 min. It is concluded that impulses from CG and RN selectively inhibit HJR, but are less effective for LJR. Depth and duration of inhibition depend essentially on parameters of CG and RN stimulation.

Animals↗
PubMed1983

[Postsynaptic potentials of motor neurons of neck muscles in the cat evoked by stimulation of the horizontal semicircular canals].

PSPs, evoked by stimulation of the ipsi- and contralateral horizontal semicircular canals (HSC) in motoneurons of neck muscles, were studied in acute experiments on cats under chloralose-nembutal anesthesia. Ipsilateral stimulation evoked EPSP with latencies ranging from 1.8 to 10.0 ms in 25 motoneurons and IPSP with latencies 1.9-3.9 ms in 10 motoneurons. Calculation of conduction time from ipsilateral canal via Deiters nucleus to neck motoneurons gives reason to consider EPSP with latencies less than 3.8 ms as disynaptic, and those with greater latencies as polysynaptic. Contralateral stimulation evoked EPSP with latencies 1.8-6.0 ms in 19 motoneurons and IPSP with latencies 3.2 and 3.9 ms in 2 motoneurons. Possible pathways conducting these influences and their functional role are discussed.

Animals↗
PubMed1981

[Excitation of motor neurons of the nucleus of the accessory nerve in cats in response to stimulation of Deiters nucleus].

Responses of the accessory motoneurons to electrical stimulation of he ipsilateral Deiters nucleus were recorded intracellularly in cats under chloralose-nembutal anesthesia. Stimulation of the Deiters nucleus evoked monosynaptic EPSP with latency from 1.3 to 2.3 ms, maximal amplitude 5.0 mV and duration from 7.0 to 10.0 ms in accessory motoneurons. Under rhythmic stimulation the EPSP were weakly potentiated and under increase in te strength of the Deiters stimuli they easily became action potentials.

Accessory Nerve↗
PubMed1980

[Monosynaptic excitation of motor neurons of the nucleus of the accessory nerve by reticulofugal impulses].

Responses of accessory motoneurons to electrical stimulation of the ipsilateral nucleus gigantocellularis of medullary reticular formation were recorded intracellularly in cats under chloraloze-nembutal anesthesia. The stimulation evoked in the accessory motoneurons monosynaptic EPSPs with latency from 0.6 to 1.0 ms, maximal amplitude 4.0 mV and duration 10 ms. Weak facilitation of EPSPs and absence of action potentials were demonstrated using paired shocks and rhythmic stimulation of the nucleus.

Accessory Nerve↗
PubMed1980

[Role of different types of infraorbital nerve fibers in synaptic activation of masticatory muscle motoneurons].

The PSPs of the masseter and digastric motoneurons evoked by stimulation of the infraorbital nerve by stimuli from 1 to 10 thresholds were studied in cats anesthetized with chloraloze and nembutal. Masseter motoneurons were divided into two groups. The first group masseter motoneurons responded to 1-2.5 threshold infraorbital nerve stimulation by short latent EPSPs. An increase in the impulse strength to 3-9 thresholds led to appearance of IPSPs with 2.8-3.5 ms latency in these motoneurons. The second group masseter motoneurons responded to 3.9 threshold stimulation of the infraorbital nerve by IPSPs with 6.8 ms latency. The strength of stimuli below 3 thresholds evoked no PSPs in these neurons. Stimuli of 1.1-2.0 thresholds evoked EPSPs in digastric motoneurons but an increased stimulation led to generation of action potentials. It is supposed that existence of different inputs is a basis for functional diversity of jaw-closing and jaw-opening reflexes.

Animals↗