[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.