title: Sex differences in serotonergic activity in dorsal and median raphe nucleus.
abstract: There is evidence on the existence of sex differences in the serotonergic system of the raphe. This study examines sex-based differences in serotonergic activity in the dorsal (DRN) and median (MRN) raphe nucleus; two structures that have consistently been implicated in the brain circuitry associated with fear and anxiety reactions. We also analyzed the effects of the elevated plus-maze (EPM) test, which allows the measuring of behavioral reactions to stress on rats produced by fear to height and open spaces on such sex differences. The present study was carried out on 70- to 80-day-old rats exposed or not to the EPM test. Immediately after the test, or 10-12 days later, groups of animals were sacrificed to measure serotonin (5-HT) and 5-hydroxyindolacetic acid (5-HIAA) concentration in the DRN and MRN, to calculate the serotonergic activity ([5-HIAA]/[5-HT]). Serotonergic activity in the female's DRN was consistently higher than in male's DRN. Such differences were not observed in the MRN. While exposed to the EPM test, female rats display more aversive responses than males, only during the day of diestrus 1. After the EPM test, serotonergic activity decreased in the female's DRN and in the male's MRN, both immediately and 10-12 days later. The sex-based differences in fear/anxiety reported in this study could be linked to the observed decrease in serotonergic activity in the DRN of female rats after the EPM test.
authors.affiliation: Laboratório de Psicobiologia, Departamento de Psicologia, FFCLRP-USP, Ribeirão Preto, Brazil. rdcasala@hotmail.com
authors.forename: Roberto
authors.initials: R
authors.lastname: Domínguez
authors.forename: Sara E
authors.initials: SE
authors.lastname: Cruz-Morales
authors.forename: Milene C
authors.initials: MC
authors.lastname: Carvalho
authors.forename: Maristela
authors.initials: M
authors.lastname: Xavier
authors.forename: Marcus L
authors.initials: ML
authors.lastname: Brandao
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D001522:Behavior, Animal; D002851:Chromatography, High Pressure Liquid; D004563:Electrochemistry / Q000379:methods; D030762:Estrous Cycle / Q000378:metabolism; D005260:Female; D006897:Hydroxyindoleacetic Acid / Q000032:analysis; D008297:Male; D018782:Maze Learning; D011903:Raphe Nuclei / Q000033:anatomy & histology / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D012701:Serotonin / Q000378:metabolism*; D012727:Sex Characteristics
chemical_list: D012701:Serotonin; D006897:Hydroxyindoleacetic Acid