Influences of central gray matter stimulation on thalamic neuron responses to high- and low-threshold stimulation of trigeminal nerve structures.

Responses of the thalamic non-specific medial nuclei and relay ventral posteromedial nucleus neurons evoked by stimulation of the teeth pulp of A alpha and A sigma fibers of infraorbital nerve and caudal nucleus of the spinal trigeminal tract were studied in cats under thiopental-chloralose anesthesia. Three groups of neurons were revealed: low-threshold, high-threshold and convergent. In medial nuclei, 29% of neurons formed the low-threshold group, 12% made up the high-threshold group and 59% were convergent.

[The suppression of the postsynaptic responses of the trigeminal nucleus motor neurons evoked by stimulation of the central gray substance of the midbrain].

Effects of the midbrain central gray matter (CGM) stimulation on responses of trigeminal motoneurons is investigated. It is shown that the conditioning CGM stimulation suppressed postsynaptic responses of motoneurons, evoked by stimulation of the tooth pulp and high-threshold fibres of the infraorbital nerve. The conditioning CGM stimulation exerts no influence on the antidromic responses of trigeminal motoneurons and jaw opening reflex, evoked by stimulation of the caudal nucleus of the spinal trigeminal tract.

[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.

[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.

[Effect of stimulation of the central gray matter of the midbrain on responses of neurons of the ventroposteromedial nucleus of the thalamus in cats].

Effect of the midbrain central gray matter (CGM) stimulation on neuronal responses of the thalamic ventro-postero-medial (VPM) nucleus evoked by stimulation of the tooth pulp, A-alpha, A-delta fibres of the infraorbital nerve and caudal nucleus of the spinal trigeminal tract have been studied in cats under thiopental-chloralose anesthesia. It is shown that the CGM stimulation by a short train of stimuli evoked excitatory responses with a latency of 30 ms in part of investigated neurons. The conditioning CGM stimulation suppressed responses in neurons of "low-threshold", "convergent" and "high-threshold" groups.

[Effect of partial transection of the medulla oblongata on inhibition of the mouth-opening reflex of the cat induced by stimulation of the mesencephalic central gray].

Effect of sections of the spinal trigeminal tract and caudal nucleus of the spinal trigeminal tract on the high-threshold jaw-opening reflex (HJR) evoked by tooth pulp stimulation and the low-threshold jaw-opening reflex (LJR) evoked by stimulation of the A-alpha infraorbital nerve fibres as well as on the suppression of these reflexes by the central grey matter was studied in cats under chloralose-nembutal anesthesia. After the trigeminal tract section HJR has increased by 8.52%.

[Effect of stimulation of the central gray substance of the midbrain on neuronal responses of the thalamic medial nuclei in the cat].

Effect of the central gray matter (CGM) stimulation on neuronal responses in the thalamic nonspecific medial nuclei evoked by stimulation of the teeth pulp, A-alpha and A-sigma fibres of the infraorbital nerve and the caudal nucleus of the spinal trigeminal tract was studied in experiments on cats under thiopental-chloralose anesthesia. Stimulation of the CGM by a train of stimuli evoked excitatory responses with latency from 15 to 40 ms in a part of investigated neurons. Conditioning stimulation of the CGM led to the inhibition of responses evoked by afferent volleys in neurons of the "low-threshold", "high-threshold" and "convergent" groups.

[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.

[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.

[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.

[Characteristics of fibers of the fastigio-spinal tract of cats].

Cord dorsum potentials (CDP) and fibre activity in the upper cervical spinal cord evoked by electrical stimulation of the contralateral fastigial nucleus of the cerebellum were recorded in cats anesthetized with chloralose and nembutal. Conduction velocity of fastigio-spinal fibres was evaluated by dividing the distance between definite cervical segments into the difference between latencies of CDP in the same segments. Fastigio-spinal fibres reach the level of C5 in ventral and ventrolateral funicles; their conduction velocities range from 20.

[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.

[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.