Reflex parasympathetic vasodilatation in facial skin.

1. The present report summarizes data from recent studies dealing with parasympathetic innervation of blood vessels in the lower lips (gingiva) of cats. 2. A study using the HRP tracing technique shows that blood vessels in the lower lip are innervated by postganglionic fibres originating in the otic ganglion, but not in the pterygopalatine ganglion. 3. There is a dual innervation of the cat lower lip by two groups of parasympathetic vasodilator fibres; in one case, fibres originating from the facial nerve root are distributed to the lower lip via chorda tympani nerve and in the other, fibres emanating from the glossopharyngeal nerve root project to the lower lip via the otic ganglion. 4. Parasympathetic reflex vasodilatation can be elicited by activation of the trigeminal (somatic), vagus (visceral), chorda tympani (gustatory) and nasal (chemical and mechanical) stimulation in the lower lips of cat. 5. Parasympathetic reflex vasodilatation elicited by somatic stimulation is mediated via the otic ganglion but not via the pterygopalatine ganglion, indicating that parasympathetic neurons, particularly those running as efferents in the glossopharyngeal nerve, are involved in the vasodilatation elicited by somatic, visceral and nasal stimulation.