[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.