Pentylenetetrazole-induced parasympathetic blood flow increase in the lower lip of the cat.

The pentylenetetrazole (30 mg/kg i.v.)-induced blood flow increase in cat lip was more marked on the sympathectomized side than on the intact side (P < 0.01). This difference is probably dependent on the degree of simultaneous activation of the sympathetic nerve elicited by pentylenetetrazole administration. The blood flow increases were markedly suppressed by prior treatment with hexamethonium (10 mg/kg i.v.), an autonomic ganglion blocker (P < 0.01). Combined section of the facial and glossopharyngeal nerve roots completely abolished the blood flow increases elicited by pentylenetetrazole administration (P < 0.01), but section of either the facial or glossopharyngeal nerve root alone failed to produce complete abolition (P < 0.05). These results indicate that the relevant parasympathetic vasodilator fibers originate not only from the glossopharyngeal, but also the facial nerves and that both participate in pentylenetetrazole-induced vasodilatation in the cat lower lip.