Localisation of mRNA for h5-HT1B and h5-HT1D receptors in human dorsal raphe

In the mammalian mesencephalon, virtually all serotoninergic neurons are lo cated in the raphe nuclei and the adjacent reticular formation. Pharmacolog ical evidence obtained in rodents suggests that terminal and somatodendriti c autoreceptors controlling serotonin (5-hydroxytryptamine, 5-HT) release b elong to the 5-HT1B/D subtype of receptors, whereas somatodendritic autorec eptors controlling neuronal cell firing are predominantly of the 5-HT1A sub type. This study investigated the presence of h5-HT1D and h5-HT1B receptor mRNA within the subdivisions of the dorsal raphe of post-mortem human brain s by means of in situ hybridisation. Although differences in the labelling intensity, which may be caused by different pre- and/or post-mortem conditi ons, were obvious among the specimens, all brains expressed both the h5-HT1 D and the h5-HT1B mRNA in dorsal raphe neurons. In comparison to h5-HT1D mR NA, expression of h5-HT1B mRNA was slightly more abundant. Information on t he existence and localisation of h5-HT1D and h5-HT1B receptors in human dor sal raphe neurons confirms that both subtypes may serve an autoreceptor fun ction in humans. This finding is of pharmacological relevance since these r eceptors are potential new targets for therapeutic interventions in psychia tric disorders such as depression and anxiety.