Apparent absence of serotonin1B receptors in biopsied and post‐mortem human brain

In order to determine if post‐mortem delays could account for the apparent absence of 5‐HT1B sites reported in human brain, 5‐HT1B 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‐HT1B 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‐HT1B 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‐HT1B type, could represent labelling to the 5‐HT1D or 5‐HT1E 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).