Relative density of 5-hydroxytryptamine receptor subtype mRNAs in female rat neuroendocrine brain determined by in situ hybridization histochemistry

The relative distribution and density of three 5-hydroxytryptamine (5-HT) receptor subtype mRNAs in female rat brain were investigated by in situ hybridization histochemistry using (36)S-labeled riboprobes. Special attention was focused on the hypothalamus and other parts of the brain involved in neuroendocrine control. Perikarya of the diagonal band of Broca (DBB), medial septum (MS), medial preoptic area (MPOA), and ventromedial hypothalamic nucleus (VMH) contained high concentrations of 5-HT(2) receptor mRNA, only moderate amounts of 5-HT(1A) receptor mRNA, and variable amounts of 5-HTP(1c) receptor mRNA. 5-HT(1c) receptor mRNA content was high in certain neurons of the lateral septum. The suprachiasmatic (SCN) and arcuate nuclei contained moderate concentrations of 5-HT(1A) receptor mRNA, but little or none of the other two subtype mRNAs. The supraoptic (SON) and paraventricular nuclei (PVN) also contained moderate amounts of 5-HT(1A) receptor mRNA, with small to moderate amounts of 5HT(1c) and 5-HT(2) receptor mRNAs. In other brain regions the highest contents of 5-HT(1A), 5-HT(1c), and 5-HT(2) receptor mRNAs were found in hippocampus, choroid plexus, and cingulate and frontal cortices, respectively. In the dorsal and median raphe nuclei 5-HT(1A) receptor mRNA content was moderately high, 5-HT(2) receptor mRNA moderate, and 5-HT(1c), receptor mRNA low. This distribution of 5-HT receptor mRNA is consistent with a role of 5-HT(2) receptors in the control of ovulation (high density in DBB, MS, and MPOA) and mating (high density in VMH) and 5-HT(1A) receptors in the 5-HT control of circadian rhythms (SCN) and in some functions of the SON and PVN.