Characterization of dihydropyridine binding sites in the rat brain: hypertension and age-dependent modulation of [3H](+)-PN 200-110 binding.

The properties of [3H]dihydropyridine (DHP), nitrendipine and (+)-PN 200-110, binding to rat cerebral membranes were investigated. In normotensive Wistar-Kyoto (WKY) adult rats, the highest densities of [3H]DHP binding sites were found in the hippocampus. Frontal cerebral cortex and hypothalamus had intermediate levels and no specific binding of [3H]DHP and [125I]iodipine could be detected in the brainstem membranes and more precisely in the nucleus tractus solitarius and in the locus coeruleus. Changes in the maximal number of DHP binding sites (Bmax) were observed in spontaneously hypertensive rats (SHR) and in old Sprague-Dawley rats. In adult SHR, there was a significant increase in the Bmax values of [3H](+)-PN 200-110 binding in the hippocampus when compared to the values obtained in WKY. There was no difference in the Bmax values between young (3 weeks) prehypertensive SHR and age-matched WKY. In senescent (26 months) Sprague-Dawley rats, the Bmax values of [3H](+)-PN 200-110 binding were significantly reduced (30%) in the frontal cerebral cortex and the hippocampus, as compared with the number of DHP binding sites found in mature Sprague-Dawley rats (15 weeks).