The study of catecholamine, acetylcholine and bradykinin in buccal circulation in dogs.

Abstract

Buccal circulation and its response to adrenaline, noradrenaline, acetylcholine and bradykinin were studied in dogs. Both common carotid arteries were perfused by the blood of the femoral artery. Buccal capillary flow in the buccal mucosa, submucosa and muscle was measured by double thermocouples.Adrenaline and noradrenaline injected into the carotid arteries caused a decrease in the buccal capillary flow and this effect of adrenaline was greater than that of noradrenaline. Adrenaline tended to cause greater reduction than noradrenaline. The decrease induced by adrenaline was more conspicuous in the buccal mucosa and submucosa, which was due to a higher sensitivity of resistance vessels in the mucosa and submucosa to adrenaline. Adrenaline reversal was observed by pretreatment with phenoxybenzamine in the buccal muscle, but not in the mucosa and submucosa.Acetylcholine caused biphasic changes, i. e., an initial increase and a delayed decrease in blood flow. The initial increase was slight in the buccal muscle, but great in the mucosa and submucosa. This effect was prevented by atropine, and also the increase in the mucosa was inhibited by phenoxybenzamine and chlorpromazine. The delayed decrease in buccal tissues induced by acetylcholine was also prevented by phenoxybenzamine, chlorpromazine and pyridinol carbamate. The effect of bradykinin on buccal circulation and its prophylactic effect were quite similar to those observed with acetylcholine. From the foregoing, our data suggests that acetylcholine causes a secondary liberation of a vasoactive kinin-like substance which may regulate the buccal capillary flow.