Gulati, A., G. Hussain, and R.C. Srimal: Effect of repeated administration of centhaquin, a centrally acting hypotensive drug, on adrenergic, cholinergic (muscarinic), dopaminergic, and serotonergic receptors in brain regions of rat. Drug Dev. Res. 23:307-323, 1991. Centhaquin, a hypotensive drug, produced a dose dependent decrease in blood pressure and heart rate in urethane anesthetized rats. The hypotensive and bradycardic effects of centhaquin were absent in cervical sectioned rats. There was no effect on blood pressure or heart rate upon intrathecal injection of centhaquin in normal rats. These results indicate that centhaquin is a centrally acting hypotensive drug with supraspinal site of action. Centhaquin (0.1 mg/kg) or its vehicle was administered orally to rats for 2 months. The blood pressure was recorded indirectly in unanesthetized rats by the plethysmographic tail cuff method. The animals were sacrificed, decapitated, and specific areas of the brain, like corpus striatum, cerebral cortex, hypothalamus, and medulla were dissected out and membranes prepared for binding studies. The mean blood pressure of rats before starting the treatment was comparable in control and treated groups. A significant decrease in mean blood pressure was observed in centhaquin treated rats. Chronic administration of cen-