A comparison of aralkylamines and aralkylguanidines as antagonists of adrenergic neurone blockade.

Abstract

Abstract Structure-activity relationships have been studied for aralkylamines and aralkylguanidines which restore the responses of the nictitating membranes to nerve stimulation in anaesthetised cats given sympathetic blocking drugs. This reversing action was largely specific for adrenergic neurone blockade; blockade of sympathetic ganglia or of α-adrenergic receptors was unaffected. (+)-Amphetamine was the most active amine and N-benzyl-N-methylguanidine was the most active guanidine. In mice, ptosis resulting from adrenergic neurone blockade was much more readily prevented or abolished by the aralkylamines and aralkylguanidines than was ptosis caused by other types of sympathetic blocking agent. The most potent antagonist of ptosis was N-(2-phenylcyclopropyl)guanidine which was about ten times as active as amphetamine. The relative antagonistic potencies of 2 amines and 8 guanidines were virtually identical for all types of adrenergic neurone blocking drug, regardless of whether or not they cause noradrenaline depletion. The prevention of guanethidine-induced ptosis was always accompanied by some reduction in the extent of heart-noradrenaline depletion, but the minimum dose of antagonist required to prevent ptosis completely was always lower than that required to eliminate depletion.