Effect of Yohimbine on the Renal Action of Clonidine in Dog

Clonidine의 개 신장작용에 대한 Yohimbine의 영향

Effect of yohimbine, a specific antagonist for presynaptic adrenoceptor, on the renal action of clonidine, a specific presynaptic adrenoceptor agonist, was investigated in dog. Clonidine, when given intravenously, produced diuretic action accompanied with augmentation of osmolar and free water clearance (Cosm and 4C_{H_2O}$), and elicited the increase of amounts of sodium and potassium excreted in urine ($E_{Na}\; and\; E_k$). These actions of clonidine were inhibited by yohimbine either injected intravenously or infused into a renal artery. Clonidine, when infused into a renal artery, produced antidiuretic action accompanied with decreased of glomerular filtration rate (GFR) and renal plasma flow (RPF), and exhibited the reduced amounts of sodium and potassium in urine. These actions of clonidine injected into a renal artery were blocked by yohimbine administered either into vein or into a renal artery. Above results suggest that yohimbine block the renal action of clonidine only in central system, do not in kidney.