title: Serotonin concentration, synthesis, cell origin, and targets in the rat caput epididymis during sexual maturation and variations associated with adult mating status: morphological and biochemical studies.
abstract: The caput epididymis of some mammals contains large quantities of serotonin whose origin, targets, and physiological variations have been poorly studied. We combined morphological and biochemical techniques to begin approaching these aspects of serotonin in the rat caput epididymis. Serotonin immunostaining was detected in mast, epithelial, and neuroendocrine cells. Epithelial cells displayed immunoreactivity to 5HT(1A), 5HT(2A,) and 5HT(3) serotonin receptors. Endothelial and mast cells labeled positive for 5HT(1B) serotonin receptors and spermatozoa displayed 5HT(2A) and 5HT(3) serotonin receptor immunoreactivity. Epithelial, endothelial, and mast cells stained positive for serotonin transporters. Only epithelial cells showed tryptophan hydroxylase immunoreactivity; this enzyme catalyzes the limiting step in the serotonin synthetic pathway. In addition, Western blot analyses of caput homogenates documented the presence of 2 protein bands ( approximately 51 kd and approximately 48 kd) that were immunoreactive for tryptophan hydroxylase. Chromatographic analyses documented the presence of tryptophan hydroxylase in the caput, and showed that both its activity and serotonin availability increased with sexual maturation and decreased following p-chlorophenylalanine treatment, an inhibitor of tryptophan hydroxylase activity. Interestingly, serotonin concentration and tryptophan hydroxylase activity tended to be higher in breeding males than in those with no mating experience. We think that these results support the existence of a local serotoninergic system in the rat caput epididymis that might regulate some aspects of male reproductive function.
authors.affiliation: Department of Cell Biology and Physiology, National Autonomous University of Mexico, Ciudad Universitaria, Mexico City.
authors.forename: Francisco
authors.initials: F
authors.lastname: Jiménez-Trejo
authors.forename: Miguel
authors.initials: M
authors.lastname: Tapia-Rodríguez
authors.forename: Daniel B C
authors.initials: DB
authors.lastname: Queiroz
authors.forename: Patricia
authors.initials: P
authors.lastname: Padilla
authors.forename: Maria Christina W
authors.initials: MC
authors.lastname: Avellar
authors.forename: Patricia Rivas
authors.initials: PR
authors.lastname: Manzano
authors.forename: Gabriel
authors.initials: G
authors.lastname: Manjarrez-Gutiérrez
authors.forename: Gabriel
authors.initials: G
authors.lastname: Gutiérrez-Ospina
mesh_terms: D000818:Animals; D004822:Epididymis / Q000166:cytology / Q000201:enzymology / Q000378:metabolism*; D010134:Fenclonine / Q000494:pharmacology; D007124:Immunoenzyme Techniques; D008297:Male; D051381:Rats; D017208:Rats, Wistar; D011985:Receptors, Serotonin / Q000378:metabolism; D012701:Serotonin / Q000096:biosynthesis / Q000378:metabolism*; D012726:Sexual Behavior, Animal; D012741:Sexual Maturation; D014365:Tryptophan Hydroxylase / Q000037:antagonists & inhibitors / Q000378:metabolism
chemical_list: D011985:Receptors, Serotonin; D012701:Serotonin; D014365:Tryptophan Hydroxylase; D010134:Fenclonine