Distribution of 5-ht5A, 5-ht5B, 5-ht6, and 5-HT7, receptor mRNAs in the rat brain

The precise involvement of 5-ht(5A), 5-ht(5B), 5-ht(6) and 5-HT7 receptors in the pleiotropic actions of 5-HT remain incompletely known. To gain insights into their physiological function(s), localization of mRNAs encoding these subtypes was carried out using in situ hybridization on rat brain sections. Localization was heterogeneous. For example, 5-ht(5A) mRNA was widely expressed while 5-ht(5B) mRNA was predominantly expressed in habenula, hippocampus and inferior olive. 5-ht(6) mRNA was abundant in olfactory tubercles and caudate putamen, and highest levels of 5-HT7 mRNA were observed in multiple thalamic nuclei. These data suggest that these receptors may have distinct functional roles within the serotonergic system. (C) 2001 Elsevier Science B.V. All rights reserved.