AbstractsBiology & Animal Science

Six sympathomimetic amines were used to investigate the postulation that the neuronal uptake process determines the sensitivity of the isolated perfused rabbit central ear artery to extra- and intraluminally applied noradrenaline and related amines. The artery was found to be more sensitive to intra- than to extraluminal noradrenaline, but the reverse was true for metaraminol, methoxamine, metanephrine, and isoproterenol. No difference was noted between the sensitivity of the artery to intra- and extraluminal phenylephrine. Drugs and procedures which impair the neuronal uptake process appeared to diminish the difference between the sensitivity of the artery to extra- and intraluminal noradrenaline, but had little or no effect on the responses of the artery to other amines. These results suggest that the neuronal uptake process is not the sole mechanism determining the sensitivity of the artery to intra- and extraluminal sympathomimetic amines.