title: Sex-specific role of a glutamate receptor subtype in a pacemaker nucleus controlling electric behavior.
abstract: Electric communication signals, produced by South American electric fish, vary across sexes and species and present an ideal opportunity to examine the bases of signal diversity, and in particular, the mechanisms underlying sexually dimorphic behavior. Gymnotiforms produce electric organ discharges (EOD) controlled by a hindbrain pacemaker nucleus (PN). Background studies have identified the general cellular mechanisms that underlie the production of communication signals, EOD chirps and interruptions, typically displayed in courtship and agonistic contexts. Brachyhypopomus gauderio emit sexually dimorphic signals, and recent studies have shown that the PN acquires the capability of generating chirps seasonally, only in breeding males, by modifying its glutamatergic system. We hypothesized that sexual dimorphism was caused by sexual differences in the roles of glutamate receptors. To test this hypothesis, we analyzed NMDA and AMPA mediated responses in PN slice preparations by field potential recordings, and quantified one AMPA subunit mRNA, in the PNs of males and females during the breeding season. In situ hybridization of GluR2B showed no sexual differences in quantities between the male and female PN. Functional responses of the PN to glutamate and AMPA, on the other hand, showed a clear cut sexual dimorphism. In breeding males, but not females, the PN responded to glutamate and AMPA with bursting activity, with a temporal pattern that resembled the pattern of EOD chirps. In this study, we have been successful in identifying cellular mechanisms of sexual dimorphic communication signals. The involvement of AMPA receptors in PN activity is part of the tightly regulated changes that account for the increase in signal diversity during breeding in this species, necessary for a successful reproduction.
authors.affiliation: Unidad Bases Neurales de la Conducta, Instituto de Investigaciones Biológicas Clemente Estable, Montevideo, Uruguay. Electronic address: lquintana@iibce.edu.uy.
authors.forename: Laura
authors.initials: L
authors.lastname: Quintana
authors.affiliation: Department of Cell and Molecular Medicine, Faculty of Medicine, University of Ottawa, Ottawa, Ontario, Canada. Electronic address: erikhg@uottawa.ca.
authors.forename: Erik
authors.initials: E
authors.lastname: Harvey-Girard
authors.affiliation: Unidad Bases Neurales de la Conducta, Instituto de Investigaciones Biológicas Clemente Estable, Montevideo, Uruguay.
authors.forename: Carolina
authors.initials: C
authors.lastname: Lescano
authors.affiliation: Unidad Bases Neurales de la Conducta, Instituto de Investigaciones Biológicas Clemente Estable, Montevideo, Uruguay.
authors.forename: Omar
authors.initials: O
authors.lastname: Macadar
authors.affiliation: Unidad Bases Neurales de la Conducta, Instituto de Investigaciones Biológicas Clemente Estable, Montevideo, Uruguay.
authors.forename: Daniel
authors.initials: D
authors.lastname: Lorenzo
mesh_terms: D000595:Amino Acid Sequence; D000819:Animal Communication; D000818:Animals; D001683:Biological Clocks / Q000187:drug effects / Q000235:genetics; D003380:Courtship; D018076:DNA, Complementary / Q000235:genetics; D004555:Electric Fish / Q000502:physiology*; D004557:Electric Organ / Q000502:physiology; D018690:Excitatory Amino Acid Agonists / Q000494:pharmacology; D005260:Female; D008297:Male; D008969:Molecular Sequence Data; D016202:N-Methylaspartate / Q000494:pharmacology; D018091:Receptors, AMPA / Q000235:genetics / Q000378:metabolism; D017470:Receptors, Glutamate / Q000235:genetics / Q000502:physiology*; D012727:Sex Characteristics; D018350:alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid / Q000494:pharmacology
chemical_list: D018076:DNA, Complementary; D018690:Excitatory Amino Acid Agonists; D018091:Receptors, AMPA; D017470:Receptors, Glutamate; D016202:N-Methylaspartate; D018350:alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid; C104722:glutamate receptor ionotropic, AMPA 2
keywords: AMPA receptors; Electrocommunication; Reproductive behavior; Sexual dimorphism