Multiple [³H]imipramine binding sites in brains of male and female Fawn-Hooded and Long-Evans rats

Comparisons of high- and low-affinity [³H]imipramine binding to whole brain homogenates from adult male and female rats of the Fawn-Hooded and Long-Evans strains were performed. Most strikingly, no significant differences were observed between the two strains in any of the binding parameters, indicating that brain [³H]imipramine binding sites, which may be related to the serotonergic uptake process, appear normal in a strain of rats with serotonin platelet storage pool disease. However, a signficant sex difference in high- but not low-affinity whole brain [³H]imipramine B_max values was observed, with females of both strains having higher densities than males. The observed sex difference in densities of high-affinity [³H]imipramine binding sites necessitates further research into possible sex hormone interactions with this binding site and serotonergic transmitter systems.