125I-lysergic acid diethylamide binds to a novel serotonergic site on rat choroid plexus epithelial cells

A binding site for lysergic acid diethylamide (LSD) on the rat choroid plexus, a brain structure that produces cerebrospinal fluid, was found to be a new type of serotonergic site. Using a high-resolution autoradiography technique, the site was localized to the epithelial cells of the choroid plexus. The density of this site was 3100 fmol/mg of protein, ten times higher than any other serotonergic site in brain homogenates. The site's pharmacology was distinct from known serotonin receptor types 5-HT1a, 5-HT1b, and 5-HT2. Binding was strongly inhibited by mianserin, serotonin, and (+)-LSD, while other serotonergic, dopaminergic, and adrenergic agents had moderate to weak effects. The site appears to be located on non-neuronal cells.

Study at a glance

Abstract

125I-Lysergic acid diethylamide (125I-LSD) binds with high affinity to serotonergic sites on rat choroid plexus. These sites were localized to choroid plexus epithelial cells by use of a novel high resolution stripping film technique for light microscopic autoradiography. In membrane preparations from rat choroid plexus, the serotonergic site density was 3100 fmol/mg of protein, which is 10-fold higher than the density of any other serotonergic site in brain homogenates. The choroid plexus site exhibits a novel pharmacology that does not match the properties of 5-hydroxytryptamine-1a (5-HT1a), 5-HT1b, or 5-HT2 serotonergic sites. 125I-LSD binding to the choroid plexus site is potently inhibited by mianserin, serotonin, and (+)-LSD. Other serotonergic, dopaminergic, and adrenergic agonists and antagonists exhibit moderate to weak affinities for this site. The rat choroid plexus 125I-LSD binding site appears to represent a new type of serotonergic site which is located on non-neuronal cells in this tissue.