Apparent absence of serotonin1Breceptors in biopsied and post-mortem human brain

Abstract

In order to determine if post-mortem delays could account for the apparent absence of 5-HT_1B sites reported in human brain, 5-HT_1B binding parameters were determined in fresh and fresh-frozen cortical biopsies and compared to results obtained in post-mortem tissues. Binding parameters and in vitro receptor autoradiography were performed by using two different ligands which have been shown to label 5-HT_1B sites, namely [³H]5-HT, in presence of 100 nM 8-OH-DPAT, and [¹²⁵I]cyanopindolol, in presence of 10 μM (–)isoproterenol. No specific binding was detected with [¹²⁵I] cyanopindolol in either fresh cortical biopsies or post-mortem tissues, suggesting that the apparent absence of 5-HT_1B receptor sites reported earlier was not related to long post-mortem delays. Some specific labelling was seen with [³H]5-HT, in presence of 8-OH-DPAT. This binding, which is unlikely to be to the 5-HT_1B type, could represent labelling to the 5-HT_1D or 5-HT_1E sites (Herrick-Davis and Titeler: J. Neurochem., 50:1624–1631, 1988; Peroutka: Trends Neurosci., 11:496–500, 1988; Titeler and Herrick-Davis: Soc. Neurosci. Abst., 14:553, 1988; Waeber et al: Neurosci. Lett., 88:11–16, 1988).