Effects of the autonomic ganglion blocking agent hexamethonium on vasodilator responses mediated by the parasympathetic ganglion on the chorda tympani pathway of the cat.

We investigated the pharmacological properties of a parasympathetic ganglion (a chorda tympani ganglion) that mediates vasodilator responses in the lower lip induced by electrical stimulation of the distal cut end of the chorda tympani or facial nerve root of the cat. These responses were suppressed by prior treatment with the autonomic ganglion blocking agent hexamethonium. We compared the effects of three doses of hexamethonium (1, 3 and 10 mg/kg, i.v.) on the chorda tympani ganglion with their effects on three large ganglia; the otic, submandibular and pterygopalatine ganglia that mediate vasodilator responses. Experiments were conducted on 20 cats weighing 1-3 kg which had been anesthetized with a mixture of urethane (100 mg/kg, i.v.) and chloralose (50 mg/kg, i.v.) then artificially ventilated (pancuronium bromide 0.2 mg/kg per h, i.v.). The chorda tympani ganglion's sensitivity to hexamethonium was similar to that of the otic ganglion but differed from the sensitivities of submandibular and pterygopalatine ganglia. We speculate that transmission through the chorda tympani ganglion is pharmacologically similar to the otic ganglion, although its precise location has yet to be determined.