Effect of cocaine on the affinity of -adrenoceptors for noradrenaline.

1. Doses of cocaine which cause specific or unspecific supersensitivity in cat spleen did not alter the blocking effect of phenoxybenzamine on the responses of isolated cat spleen strips to noradrenaline.2. The same doses of cocaine did not increase the protection of alpha-adrenoceptors given by noradrenaline during a standard exposure to phenoxybenzamine.3. It is concluded that cocaine does not change the affinity of the alpha-adrenoceptor for noradrenaline, and therefore changes in affinity are not responsible for the potentiating action of cocaine.