Immunohistochemical Visualization of 5-HT1AReceptors in the Rat Brain

Anti-5-HT receptor antibodies were raised by injecting rabbits with either a synthetic peptide corresponding to the aa 243-268 portion of the third intracellular loop of the rat 5-HTAreceptor, or a fusion protein made of the complete loop (aa 216-350) coupled to glutathione-S-transferase. Immunohistochemical staining with these antibodies allowed the visualization of 5-HTAreceptors mainly in the limbic areas and anterior raphe nuclei, as expected from previous autoradiographic data with selective 5-HTAreceptor radioligands. Double immunostainingwith anti-5-HT,, receptor antibodies and anti-5-HT or anti-choline acetyl-transferase antibodies demonstrated that these receptors are located in the plasma membrane of practically all serotoninergic neurones in anterior raphe nuclei and a small fraction of cholinergic neurones in the median septum.