title: Regional and subtype-specific loss of GnRH neurons is associated with diminished mating behavior in middle-aged male rats.
abstract: The current study was to examine the relationship between the number of gonadotropin-releasing hormone (GnRH) neurons and male sexual behavior in middle-aged rats. Based on their sexual performance, middle-aged male rats (18-19 months) were assigned to three groups: (i) Group MIE (showing mounts, intromissions, and ejaculation), (ii) Group MI (displaying mounts and intromissions, but no ejaculation), and (iii) Group NC (showing no copulatory behavior). The brains of these middle-aged animals and of sexually active, young controls were collected and then examined for immunohistochemical localization of GnRH neurons. The numbers of two subtypes of GnRH neurons, smooth (s-GnRH) and irregular (i-GnRH), in the medial septum (MS), organum vasculosum of the lamina terminalis (OVLT), preoptic area (POA), and anterior hypothalamus (AH), were determined under a light microscope. As compared to young controls, an age-related decrease in the number of s-GnRH neurons was found in the MS of MIE rats. Among three groups of middle-aged rats, Groups MIE and MI had more s-GnRH neurons in the POA and i-GnRH neurons in the OVLT and POA than Group NC. In addition, loss of s-GnRH and i-GnRH neurons in the MS was observed in Groups MI and NC and Group NC, respectively. Our results suggest that a decrease in GnRH neuron subtypes occurring in different brain regions might be critical for the loss of specific components of male rat sexual behavior during aging.
authors.affiliation: Department of Biological Sciences, California State University, Long Beach, Long Beach, CA, USA.
authors.forename: Houng-Wei
authors.initials: HW
authors.lastname: Tsai
authors.forename: Yuan-Feen
authors.initials: YF
authors.lastname: Tsai
authors.forename: Mei-Yun
authors.initials: MY
authors.lastname: Tai
authors.forename: Kuei-Ying
authors.initials: KY
authors.lastname: Yeh
mesh_terms: D000375:Aging / Q000378:metabolism*; D000818:Animals; D002452:Cell Count; D007987:Gonadotropin-Releasing Hormone / Q000378:metabolism*; D007031:Hypothalamus / Q000378:metabolism*; D008297:Male; D009474:Neurons / Q000378:metabolism*; D051381:Rats; D020318:Rats, Long-Evans; D020665:Septum of Brain / Q000378:metabolism*; D012726:Sexual Behavior, Animal / Q000502:physiology*
chemical_list: D007987:Gonadotropin-Releasing Hormone
keywords: Aging; GnRH; Immunohistochemistry; Rat; Sexual behavior