Antidiuretic effects of ATP induced by microinjection into the hypothalamic supraoptic nucleus in water-loaded and ethanol-anesthetized rats.

The effects of microinjection of purinoceptor agonists into the hypothalamic supraoptic nucleus (SON) on urination were examined in water-loaded and ethanol-anesthetized rats. Adenosine triphosphate (ATP), but neither adenosine diphosphate (ADP), adenosine monophosphate (AMP) nor adenosine, concentration-dependently decreased the urine outflow with concomitant increase in the urine osmotic pressure. The ED50 value for ATP was approx. 60 nmol. The antidiuretic effect of ATP was blocked either by prior injection of theophylline (an antagonist of the P1-type purinoceptor) or by intravenous administration d(CH2)5-D-Tyr(Et)-valine-arginine-vasopressin (VAVP). These results suggest that ATP injected into the SON has antidiuretic effects due to release of AVP through an activation of theophylline-sensitive purinoceptors.