Effects of alpha-2-adrenoceptor agonists on induced diuresis in rats

The alpha-2 adrenoceptor agonists, clonidine, guanabenz, and guanfacine, injected subcutaneously produced a dose-related diuresis. The maximal effect occurred at 2h after administration of clonidine 192 micrograms/kg or 960 micrograms/kg of guanabenz and guanfacine. The alpha-2 antagonist, yohimbine, in doses of 1-8 mg/kg administered prior to the agonists caused a dose-dependent decrease in urine output. The action of the three agonists at alpha-2 adrenoceptors was supported by the observation that the alpha-1 adrenoceptor agonist, prazosin (0.61-2.5 mg/kg), administered prior to each agonist caused an inconsistent decrease in the elevated urinary output caused by clonidine, guanabenz and guanfacine. These results indicate that stimulation of alpha-2 adrenoceptors causes diuresis in the rat.