Differential Serotonin2 Receptor Recovery in Mature and Senescent Rat Brain after Irreversible Receptor Modification: Effect of Chronic Reserpine Treatment1

We report here the differential time course of recovery of [3H] ketanserin-labeled serotonin2 (5-HT2) receptors in frontal cortex of mature (4 months d) and senescent (28 months old) male Fischer 344 rats. We provide evidence that the irreversible modification of 5-HT2 serotonin receptors by N-ethoxycarbonyl-2-ethoxy-1,2-dihydroquinoline occurs at the ligand binding site and that this treatment does not appear to affect the interaction of these receptors with their guanine nucleotide regulatory pro-tein. Senescent rats exhibited significantly reduced (-20%) max-imum receptor density levels of 5-HT2 receptors compared with their mature counterparts. The time course of recovery of [3H] ketanserin binding to 5-HT2 receptors after irreversible receptor modification by a single peripheral injection of N-ethoxycarbonyl-2-ethoxy-1,2-dihydroquinoline was significantly slower in senes