The changes of serotonin (5HT-1, 5HT-1A, 5HT-1B, 5HT-2) receptor densities in rat brain following chronic zotepine treatment.

The changes of serotonin (5HT-1, 5HT-1A, 5HT-1B and 5HT-2) receptor densities following a chronic zotepine (ZTP) alone or combined lithium (Li)-ZTP treatment were investigated in several regions of the rat brain. As a result, the densities of the 5HT-2 receptors in the frontal cortex (FC) decreased remarkably and those of the 5HT-1 and 5HT-1A receptors in the striatum (ST) increased in the ZTP alone group and the combined Li-ZTP group compared with the saline group. None of the serotonin receptors changed in the hippocampus (HIP). Judging from these findings, we suppose that the decreases of the 5HT-2 receptors in FC may have been induced not only by the chronic antidepressant treatment, but also by the other chronic 5HT-2 antagonist (ZTP, chlorpromazine, etc.) treatment. In addition, the increases of the 5HT-1 and 5HT-1A receptors in ST may not have been associated with ZTP's clinically potent antimanic effect because of a lack of Li's enhancement in the changes of the 5HT-1 and 5HT-1A receptors in contrast to its clinical effect and a lack of the changes in the 5HT-1B receptors where ZTP may have acted potently in vitro.