| Abstract: | 1. The action of choline on the vasoconstrictor responses of the perfused mesenteric arteries of the rat to sympathetic nerve stimulation and to injected noradrenaline has been investigated.2. The infusion of choline (500 mug/ml), for periods of 15 s, increased the response to sympathetic nerve stimulation, whereas the infusion of the same concentration for 20 min greatly reduced the response to nerve stimulation. Choline (up to 500 mug/ml), infused either for short or long periods, did not alter the response to injected noradrenaline.3. The inhibitory action of choline on the response to nerve stimulation was abolished either by an increase in the calcium concentration from 1.8 to 5.4 mM or by simultaneous infusion of (+)-amphetamine or atropine.4. The results suggest that choline in concentrations of 500 mug/ml has the same effect on adrenergic transmission in mesenteric arteries as acetylcholine at concentrations of 5 ng/ml. |
