ACTIONS OF PIPERIDINE AND DIMETHYLPHENYLPIPERAZINIUM (DMPP) ON AFFERENT DISCHARGES OF THE CATS CAROTID-BODY

Chemoreceptor discharges were recorded in vivo from fine filaments of carotid sinus nerve; their frequency was used as index of receptor activity. Effects of piperidine on chemoreceptors were studied and compared with those of dimethylphenylpiperazinium (DMPP) on chemoreceptors in adult cats. Intracarotid-arterial injections of piperidine produced a transient increase in chemoreceptor discharges, the threshold dose ranging from 10 to 50 μg i.a. The excitatory effect of piperidine was not affected by atropine, heamethonium or GABA. DMPP (0.2-0.5 μ i.a.) induced a marked increase in chemoreceptor discharges, which was abolished by hexamethonium, but not by atropine. DMPP (2-5 μg i.a.) induced sinus baroreceptor excitation, but piperidine did not. The results indicate that piperidine exerted excitatory effects on carotid body chemoreceptors, possibly acting on nerve endings of chemoreceptor afferent fibers. © 1979.