EFFECTS OF ACETYLCHOLINE AND CARBACHOL ON THE BLOOD VESSELS OF THE FROG

¹ Department of Pharmacology, College of Medical Sciences, Banaras Hindu University, Varanasi-5, India

The effects of a few cholinergic agents, especially acetylcholine and carbachol, were studied on the perfused systemic blood vessels of the frog. Nicotine, adrenaline, isoprenaline, papaverine and barium chloride were used as controls. Acetylcholine (ACh) and carbachol (CCh) were found to be potent vasoconstrictors, confirming the report of Rahman [1963] with ACh. The vasoconstrictor action of choline and pilocarpine was much weaker. The ACh action was only partially inhibited by pentolinium, but the actions of ACh as well as CCh remained unaffected by tolazoline, gallamine and d-tubocurarine. Atropine nearly completely blocked the vasoconstrictor responses of ACh and CCh though the skeletal muscle spasms caused by these choline esters remained unaffected. The results indicate that the nicotinic activity of ACh and CCh did not play any major role in the vasoconstrictor actions in frogs. Decrease in perfusion rate was also not due to spasms of skeletal or non-vascular smooth muscle. It appeared that the action is chiefly mediated through atropine sensitive receptors.

Note:

The authors are grateful to Mr O. P. Yadav for technical assistance.