Comparative anatomical distribution of 5-HT1A receptor mRNA and 5-HT1A binding in rat brain--a combined in situ hybridisation/in vitro receptor autoradiographic study

• Published in: Brain research Vol. 561; no. 1; p. 51
• Main Authors: Chalmers, D T, Watson, S J
• Format: Journal Article
• Language: English
• Published: Netherlands 04.10.1991
• Subjects: Animals; Autoradiography; Brain - metabolism; Densitometry - methods; Diencephalon - metabolism; Male; Mesencephalon - metabolism; Nucleic Acid Hybridization; Rats; Rats, Inbred Strains; Receptors, Serotonin - genetics; Receptors, Serotonin - metabolism; RNA Probes; RNA, Messenger - metabolism; Serotonin - metabolism; Telencephalon - metabolism
• ISSN: 0006-8993
• DOI: 10.1016/0006-8993(91)90748-K

The present study examined the comparative distribution of 5-HT1A receptor mRNA and 5-HT1A receptors in rat brain using a combination of in situ hybridisation histochemistry and in vitro receptor autoradiography. 5-HT1A mRNA was visualized using a 910 bp cRNA probe synthesised from a BalI-PvuII fragment of the rat 5-HT1A reetor gene, while 5-HT1A receptors were labelled with the 5-HT1A-selective ligand 8-OH-DPAT. In general terms, there was a complementary distribution of cells expressing 5-HT1A receptor mRNA and 5-HT1A receptor sites. High levels of both 5-HT1A mRNA and 5-HT1A receptors were evident in the hippocampal formation (CA1, CA3, dentate gyrus), entorhinal cortex, and raphe nuclei and lower levels in neocortex and thalamus. Although 5-HT1A mRNA was not expressed in any regions which did not also exhibit 5-HT1A receptors, within both the diagonal band and the medial septal nucleus mRNA levels were proportionately higher than 5-HT1A receptor levels, possibly reflecting receptor transport or a heterogeneity in 5-HT1A receptor turnover mechanisms. 5-HT1A receptor mRNA and 5-HT1A binding sites were undetectable in caudate/putamen and cerebellar regions. The present data indicate the synthesis of 5-HT1A receptors both in raphe serotonergic cells and anatomically specific serotonergic projection areas, further supporting both a presynaptic autoregulatory and postsynaptic modulatory role for this receptor in serotonergic transmission.