title: Testosterone increases the number of substance P-like immunoreactive neurons in a specific sub-division of the lateral hypothalamus of the weakly electric, brown ghost knifefish, Apteronotus leptorhynchus.
abstract: During spawning, male and female brown ghost knife fish modulate their electric organ discharge to produce discrete courtship signals known as chirps. However, non-spawning fish show clear sex differences in chirp responsiveness to electrosensory stimuli; males consistently chirp, whereas females do not. This behavioral dimorphism is paralleled by sex differences in substance P-like immunoreactivity (SPl-ir) in the prepacemaker nucleus (PPn) which regulates chirping. The PPn is densely innervated by SPl-ir fibers in males, but not in females. However, we have shown that both female chirping behavior and the expression of SPl-ir in the PPn are enhanced following adult testosterone treatment [J.G. Dulka, L. Maler, W. Ellis, Androgen-induced changes in electrocommunicatory behavior are correlated with changes in substance P-like immunoreactivity in the brain of the electric fish, Apteronotus leptorhynchus, J. Neurosci. 15 (1995) 1879-1890]. Thus, testosterone-induced changes in SPl-ir input to the PPn may modulate female chirping during spawning. Recent evidence suggests that SPl-ir projections to the PPn may originate from SPl-ir neurons in the lateral hypothalamus (Hl). If so, one might expect to see a greater number of SPl-ir neurons in the Hl of testosterone-implanted females compared to Blank-implanted controls. In making this comparison, we found that both groups of females had similar numbers of SPl-ir neurons in the anterior Hl, but that testosterone-implanted females had significantly (p<0.01) more SPl-ir neurons in a distinct part of the posterior Hl. This sub-population of testosterone-sensitive, SPl-ir neurons may contribute to the regulation of chirping, since an increase in their number is positively correlated with the appearance of SPl-ir fibers in the PPn [J.G. Dulka, L. Maler, W. Ellis, Androgen-induced changes in electrocommunicatory behavior are correlated with changes in substance P-like immunoreactivity in the brain of the electric fish, Apteronotus leptorhynchus, J. Neurosci. 15 (1995) 1879-1890].
authors.affiliation: Department of Biology, Nebraska Behavioral Biology Group, Creighton University, Omaha, NE 68178, USA. jdulka@creighton.edu
authors.forename: J G
authors.initials: JG
authors.lastname: Dulka
authors.forename: S L
authors.initials: SL
authors.lastname: Ebling
mesh_terms: D000818:Animals; D018931:Antineoplastic Agents, Hormonal / Q000494:pharmacology*; D001522:Behavior, Animal / Q000187:drug effects; D001923:Brain Chemistry / Q000187:drug effects; D002452:Cell Count; D004555:Electric Fish; D005260:Female; D007026:Hypothalamic Area, Lateral / Q000166:cytology*; D008297:Male; D009412:Nerve Fibers / Q000737:chemistry; D009473:Neuronal Plasticity / Q000187:drug effects; D009474:Neurons / Q000737:chemistry* / Q000166:cytology / Q000648:ultrastructure; D012727:Sex Characteristics; D013373:Substance P / Q000032:analysis*; D013739:Testosterone / Q000494:pharmacology*; D014828:Vocalization, Animal / Q000187:drug effects
chemical_list: D018931:Antineoplastic Agents, Hormonal; D013373:Substance P; D013739:Testosterone