Vol. 56, Issue 3, 552-561, September 1999

Pharmacological and Molecular Characterization of 5-Hydroxytryptamine₇ Receptors in the Rat Adrenal Gland

Vincent Contesse, Sebastien Lenglet, Luca Grumolato, Youssef Anouar, Isabelle Lihrmann, Herve Lefebvre, Catherine Delarue, and Hubert Vaudry

European Institute for Peptide Research (Institut Fédératif de Recherches Multidisciplinaires sur les Peptides 23), Laboratory of Cellular and Molecular Neuroendocrinology, Institut National de la Santé et de la Recherche Médicale, Unité Associée Centre National de la Recherche Scientifique, University of Rouen, Mont-Saint-Aignan, France

Serotonin (5-hydroxytryptamine; 5-HT) is a potent stimulator of aldosterone secretion in the rat adrenal gland but the type of receptor involved in the mechanism of action of 5-HT remains unknown. The aim of the present study was to determine the pharmacological profile and to clone the receptor responsible for the corticotropic effect of 5-HT in rat glomerulosa cells. A series of 10 serotonergic receptor agonists and 12 receptor antagonists was used to characterize the receptor mediating the effect of 5-HT on aldosterone secretion from perifused rat adrenocortical slices. Correlation analysis between the potencies of the different compounds in our model and those previously reported for various recombinant 5-HT receptors showed that the rat adrenal 5-HT receptor exhibits the same pharmacological profile as the 5-HT₇ receptor transiently expressed in COS-7 cells (r = 0.82 for agonists, p < .05; r = 0.83 for antagonists, p < .01). Polymerase chain reaction with specific primers revealed the expression of 5-HT₇ receptor mRNA in the rat adrenal gland. Cloning of the polymerase chain reaction product confirmed that the amplified DNA corresponded to the 5-HT₇ receptor cDNA sequence. Western blot analysis showed the presence of a protein with an apparent molecular mass of 66 kDa in the adrenal cortex but not in the medulla. Taken together, these data demonstrate that the rat adrenal glomerulosa expresses functional 5-HT₇ receptors. Rat glomerulosa cells will thus provide a robust and sensitive bioassay for future studies on native 5-HT₇ receptors.