Inefficiency of isoprenaline to induce drinking in the goat

Isoprenaline, which acts as a potent dipsogen in water-satiated rats and dogs, did not elicit water intake when infused intravenously at 0.1 or 0.3 mu/kg min-1 in non-hydrated goats. Even the low dose of the drug caused a marked reduction of parotid salivary flow. The possibility is discussed that reduced salivary secretion might be the particular effect which makes isoprenaline dipsogenic in prandially drinking species. The intravenous infusion of isoprenaline at the high dose level caused an inhibition of the water diuresis of hydrated goats, concomitant with reduced renal Na+ excretion and a marked, sustained fall in the arterial blood pressure. Significant amounts of ADH were recovered from the urine secreted during the antidiuresis. This ADH-release was apparently not due to central beta-adrenergic stimulation since no inhibition of the water diuresis was observed during intraventricular infusions of isoprenaline. Rather, the ADH-release appears to have been secondary to the isoprenaline-induced fall in arterial blood pressure.