Printed in U.S.A. THE ANTAGONISM BY ATROPINE OF THE RESPONSE OF THE NICTITATING MEMBRANE TO SYMPATHETIC NERVE STIMULATION1

RRAs, H. W. AND T. H. TSAI: The antagonism by atropine of the response of the nictitating membrane to sympathetic nerve stimulation. J. Pharmacol. 152: 186-196, 1966. The antagonism by atropine of the response of the nictitating membrane to nerve stimula-tion is not due to the antagonism by atropine of acetylcholine. This is demonstrated by the following observations on the nictitating membrane: 1) more than a 100-fold larger dose of atropine was necessary to reduce a particular response to sympathetic nerve stimulation than to antagonize the same response to acetylcholine; 2) the minimal dose of atropine required to reduce a particular response to nerve stimulation was identical with the minimal dose required to antagonize the same response to epinephrine; 3) when responses of equal magnitude were compared, atropine was equieffective against nerve stimulation in normal and reserpine-pretreated preparations; and 4) scopolamine did not antagonize the response to nerve stimulation. The antagonism of atropine to sympatho-mimetic amines is of the surmountable type. Atropine exerted its antagonistic effects on the nictitating membrane of the cat and of the rabbit; on the blood pressure and the hear