Modification of the vascular response to isoprenaline by cholinomimetic drugs

Abstract

1 Pilocarpine and other cholinomimetic drugs convert isoprenaline to a vasoconstrictor and pressor agent. 2 This effect of pilocarpine was abolished by atropine; it is thus an acetylcholine-like response. It was not dependent on the integrity of the central nervous system or the adrenal glands and was not abolished by ganglionic blockade. 3 The constrictor action of isoprenaline after pilocarpine was abolished by propranolol; this action of isoprenaline is thus on the β-adrenoceptor. Another β-adrenoceptor stimulating agent, salbutamol, resembled isoprenaline in this situation, though papaverine and acetylcholine did not. 4 The constrictor action of isoprenaline after pilocarpine was abolished by phenoxybenzamine, guanethidine and cocaine; the effect did not appear after reserpine pretreatment. 5 These results suggest an action of cholinomimetic drugs at adrenergic nerve endings which permits the uptake of β-adrenoceptor stimulating agents resulting in the release of neuronal transmitter.