[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.