GABA and benzodiazepine binding sites in spontaneously hypertensive rat

The binding of GABA to its central receptor sites and of benzodiazepines to central and peripheral types of binding sites was compared in age-matched spontaneously hypertensive rat (SHR) and normotensive (WKY) rat. The KD and Bmax values of GABA agonist binding were not significantly different between SHR and WKY rat in the forebrain, cerebellum or pons-medulla. The binding of [3H]flunitrazepam to central types of binding sites was also not different in 12 week-old SHR and WKY rat. However, the binding of [3H]flunitrazepam and [3H]RO5-4864 was significantly lower in the SHR kidney, as compared to WKY rat kidney. This decrease was due to a lower Bmax in SHR kidney. In contrast, the binding of these radioligands in the hearts of the two strains was not different. These results indicate that the SHR has lower peripheral benzodiazepine binding sites in the kidney as compared to age-matched normotensive WKY rat kidney.