Effects of chemical sympathectomy with 6-hydroxydopamine on α- and β-adrenoceptors and muscarinic cholinoceptors in rat kidney

The autonomic receptors in the rat kidney were characterized using the radioligands [³H]prazosin, [³H]clonidine, [³H]dihydroalprenolol (DHA) and [³H]quinuclidinyl benzilate (QNB). The specific binding of [³H]prazosin, [³H]clonidine, [³H]DHA and [³H]QNB to rat kidney membranes was saturable and of high affinity, and showed a pharmacological specificity as well as stereospecificity which characterized renal α₁-, α₂- and β-adrenoceptors and muscarinic cholinoceptors, respectively. There was a relatively greater density of α-adrenoceptors than β-adrenoceptors or muscarinic cholinoceptors in the rat kidney. Chemical sympathectomy of rats with 6-hydroxydopamine. HBr (6-OHDA, 50 × 2 mg/kg i.v., 24 h interval) caused a significant increase (21-56%) in the B_max values for renal [³H]prazosin, [³H]clonidine and [³H]DHA binding at 1 and 2 weeks following the treatment, without a change in the K_d values. 6-OHDA treatment had no significant effect on the K_d and B_max values for [³H]QNB binding at 1-3 weeks after the treatment. The norepinephrine (NE) concentration was reduced (68-76%) in the 6-OHDA-treated rat kidney. In conclusion, the present study provides biochemical evidence for the possible localization of postsynaptic α₁-, α₂- and β-adrenoceptors and muscarinic cholinoceptors in the rat kidney and also for the regulation of these adrenoceptors by the sympathetic nervous system.