Abstract

Amodiaquin and chloroquine produced characteristic dose-related pressor responses in anesthetized dogs pretreated with methylamphetamine; treatment with tolazoline or dibozane with pronethalol prevented these responses. The pressor responses were not affected by atropine, by xylocholine or by P-286; however, they were augmented by hexamethonium. In dogs pretreated with reserpine the pressor responses to amodiaquin and chloroquine were severely reduced; an infusion of norepinephrine did not restore the responses. The 4-aminoquinolines injected intravenously into the dog or injected directly into the "external circuit" caused only a transient relaxation of the rat stomach strip bathed in blood; the pressor effect evoked by the 4-aminoquinolines after methylamphetamine pretreatment of the dogs was not accompanied by relaxation of the stomach strip. It is suggested that the pressor effect of these compounds is mediated, to a large extent, through a release of catecholamines from the tissue stores but seemingly not from adrenal medulla, and that the amines are released in the vicinity of receptor sites and not into the general circulation.