title: An immunohistochemical study of the gonadotrophin-releasing hormone 1 system in solitary Cape mole-rats, Georychus capensis, and social Natal mole-rats, Cryptomys hottentotus natalensis.
abstract: Mole-rat species within the family Bathyergidae exhibit a wide range of reproductive strategies and social systems. Various forms of reproductive suppression are displayed within this family: in the solitary species, breeding is suspended for part of the year and in the social species, reproduction is suppressed in subordinate animals. This study investigated the gonadotrophin-releasing hormone 1 (GnHR-1) systems of breeding and non-breeding solitary Cape mole-rats and social Natal mole-rats for possible inter- and/or intra-species differences. In both species, GnRH-1 cell bodies are predominantly in the medial septum region of the diagonal band or the preoptic area, with relatively few in the mediobasal hypothalamus; a dense concentration of GnRH-1-immunoreactive (ir) processes is present in the region of the organum vasculosum of the lamina terminalis. In Cape mole-rats, GnRH-1-ir processes are particularly dense within the lateral margins of the median eminence, which is enfolded by a large pars tuberalis of the pituitary gland. Natal mole-rats display GnRH-1-ir processes across the breadth of the median eminence, which is abutted by a relatively small pars tuberalis. There are more GnRH-1-ir cell bodies in Natal mole-rats than in Cape mole-rats ( approximately 720 vs. approximately 420). No significant differences were found in the number, distribution or size of GnRH-1-ir cell bodies according to season in Cape mole-rats or according to reproductive status or sex in Natal mole-rats. In female and male Natal mole-rats, GnRH-1-immunoreactivity in the median eminence is less dense in the reproductive animals; no such difference was found in Cape mole-rats between the breeding and non-breeding seasons. These immunohistochemical results are discussed in the light of earlier studies which identified no functional neuroendocrine impediments underlying regulated reproduction in either Cape or Natal mole-rats. The cumulative findings suggest that the principal factors determining seasonal or socially induced suppression of reproduction in these species are behavioral rather than neuroendocrine.
authors.affiliation: Mammal Research Institute, Department of Zoology and Entomology, University of Pretoria, Pretoria, 0002, South Africa. moosthuizen@zoology.up.ac.za
authors.forename: M K
authors.initials: MK
authors.lastname: Oosthuizen
authors.forename: N C
authors.initials: NC
authors.lastname: Bennett
authors.forename: C W
authors.initials: CW
authors.lastname: Coen
mesh_terms: D000818:Animals; D002452:Cell Count; D005260:Female; D007987:Gonadotropin-Releasing Hormone / Q000378:metabolism* / Q000494:pharmacology; D007030:Hypothalamo-Hypophyseal System / Q000187:drug effects / Q000502:physiology; D007031:Hypothalamus / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D007150:Immunohistochemistry; D007986:Luteinizing Hormone / Q000097:blood; D019577:Mole Rats; D012098:Reproduction / Q000502:physiology; D012621:Seasons; D012726:Sexual Behavior, Animal / Q000187:drug effects / Q000502:physiology*; D013045:Species Specificity
chemical_list: D007987:Gonadotropin-Releasing Hormone; D007986:Luteinizing Hormone