Localization and gene expression of serotonin 1A (5HT1A) receptors in human brain postmortem

We investigated the binding parameters, i.e. the maximum binding capacity (Bmax) and the dissociation constant (Kd), of [3H]8-hydroxy-2-(di-N-propylamino)tetralin ([3H]8-OH-DPAT) labeling the serotonin receptor of the 1A type (5HT1A), and the distribution of the mRNA encoding it in some human brain areas obtained from autoptic samples. The results showed that the Bmax was significantly higher in the hippocampus than in the prefrontal cortex and the striatum, while the Kd had the inverse, although not significant, pattern. The expression study revealed that 5HT1A mRNA distribution in the hippocampus and prefrontal cortex was consistent with the data of the [3H]8-OH-DPAT binding. A different result was obtained in the striatum where no 5HT1A mRNA expression was detected, despite the measurement of specific [3H]8-OH-DPAT binding. These findings underline the different nature of [3H]8-OH-DPAT binding sites in different brain areas and the need for further studies on 5HT receptor gene expression in human brain.