The inhibitory effect of guanabenz on submandibulary salivation induced by chorda tympani stimulation in anaesthetized cat.

The actions of guanabenz, an alpha 2-adrenoceptor agonist, on submandibulary salivation were examined in the anaesthetized cat. Guanabenz reduces submandibulary salivation evoked by electrical stimulation of the chorda tympani in dose and frequency dependent manner. This effect was antagonized by yohimbine but not by prazosin. Guanabenz increased salivation elicited by intraarterial injection of carbachol. This potentiated effect was suppressed by yohimbine, but not by prazosin. On noradrenaline induced salivation guanabenz has no effect, while prazosin virtually abolished it, indicating involvement of alpha 1-adrenoceptors. It appears that guanabenz reduces peripheral parasympathetically evoked submandibulary salivation influencing the presynaptic control of transmitter release alpha 2-adrenoceptors. Postsynaptic alpha 2-adrenoceptors are not involved in the inhibition of salivation by this agent.