d -Tubocurarine as a Dopaminergic Antagonist in the Rabbit Ear Artery

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Abstract
D-Tubocurarine inhibits the action of dopamine on mollusk neurons. Whether or not d-tubocurarine acts as an antagonist on mammalian dopamine receptors was studied. The isolated, perfused rabbit ear artery was the experimental preparation used. Dopamine and apomorphine produced concentration-dependent inhibition of the response to electrical field stimulation of the periarterial sympathetic nerves. d-Tubocurarine antagonized the inhibitory effect of dopamine and apomorphine in a competitive manner. The calculated dissociation constants for d-tubocurarine acting against dopamine and apomorphine were 1.9 .+-. 0.6 .mu.M and 1.7 .+-. 0.5 .mu.M, respectively. d-Tubocurarine (1-100 .mu.M), by itself, did not affect the response of the artery to sympathetic nerve stimulation. The nicotinic antagonists hexamethonium, pancuronium and mecamylamine did not affect the dopamine action. d-Tubocurarine could apparently attenuate the therapeutic benefit of dopamine if both of these drugs are administered concomitantly.