RELATIVE DENSITY OF 5-HYDROXYTRYPTAMINE RECEPTOR SUBTYPE MESSENGER-RNAS IN FEMALE RAT NEUROENDOCRINE BRAIN DETERMINED BY INSITU 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 36S-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-HT2 receptor mRNA, only moderate amounts of 5-HT1A receptor mRNA, and variable amounts of 5-HTP1c receptor mRNA. 5-HT1c receptor mRNA content was high in certain neurons of the lateral septum. The suprachiasmatic (SCN) and arcuate nuclei contained moderate concentrations of 5-HT1A 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-HT1A receptor mRNA, with small to moderate amounts of 5HT1c and 5-HT2 receptor mRNAs. In other brain regions the highest contents of 5-HT1A, 5-HT1c, and 5-HT2 receptor mRNAs were found in hippocampus, choroid plexus, and cingulate and frontal cortices, respectively. In the dorsal and median raphe nuclei 5-HT1A receptor mRNA content was moderately high, 5-HT2 receptor mRNA moderate, and 5-HT1c, receptor mRNA low. This distribution of 5-HT receptor mRNA is consistent with a role of 5-HT2 receptors in the control of ovulation (high density in DBB, MS, and MPOA) and mating (high density in VMH) and 5-HT1A receptors in the 5-HT control of circadian rhythms (SCN) and in some functions of the SON and PVN. © 1992.