Drinking and antidiuresis elicited by isoprenaline in the dog

1. Isoprenaline hydrochloride injected subcutaneously or infused intravenously caused drinking and simultaneous antidiuresis in the dog. The minimal effective dose was between 20 and 50 mug per dog.2. Isoprenaline-induced drinking was prevented by the beta-adrenergic antagonist propranolol and enhanced by the alpha-antagonist phentolamine.3. Ganglionic blockade with pentolinium or with hexamethonium did not interfere with the response.4. A delay of 1 hr after injection of 100 mug isoprenaline, before drinking was permitted, did not significantly reduce the amount of water subsequently drunk. A preload of water approximately equal to the volume of water normally drunk caused a greater reduction in water intake in some dogs.5. Isoprenaline caused an increase in heart rate and pulse pressure which lasted for between 1 and 3 hr according to dose. Central venous pressure fell, but mean arterial pressure was little altered. Haemodynamic changes preceded drinking by about 5 min.6. Infusion of isoprenaline caused drinking in the bilaterally nephrectomized dog.7. We conclude that isoprenaline is a potent stimulus to drinking in the dog and that the effect is not exclusively mediated by the renin-angiotensin system.