Analysis of gonadotrophin-releasing hormone-1 and kisspeptin neuronal systems in the nonphotoregulated seasonally breeding eastern rock elephant-shrew (Elephantulus myurus)

Katarina Medger*, Nigel C. Bennett, Christian T. Chimimba, Maria K. Oosthuizen, Jens D. Mikkelsen, Clive W. Coen

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

3 Citations (Scopus)

Abstract

Of the 18 sub-Saharan elephant-shrew species, only eastern rock elephant-shrews reproduce seasonally throughout their distribution, a process seemingly independent of photoperiod. The present study characterizes gonadal status and location/intensity of gonadotrophin-releasing hormone-1 (GnRH-1) and kisspeptin immunoreactivities in this polyovulating species in the breeding and nonbreeding seasons. GnRH-1-immunoreactive (ir) cell bodies are predominantly in the medial septum, diagonal band, and medial preoptic area; processes are generally sparse except in the external median eminence. Kisspeptin-ir cell bodies are detected only within the arcuate nucleus; the density of processes is generally low, except in the septohypothalamic nucleus, ventromedial bed nucleus of the stria terminalis, arcuate nucleus, and internal and external median eminence. Kisspeptin-ir processes are negligible at locations containing GnRH-1-ir cell bodies. The external median eminence is the only site with conspicuously overlapping distributions of the respective immunoreactivities and, accordingly, a putative site for kisspeptin's regulation of GnRH-1 release in this species. In the nonbreeding season in males, there is an increase in the rostral population of GnRH-1-ir cell bodies and density of GnRH-1-ir processes in the median eminence. In both sexes, the breeding season is associated with increased kisspeptin-ir process density in the rostral periventricular area of the third ventricle and arcuate nucleus; at the latter site, this is positively correlated with gonadal mass. Cross-species comparisons lead us to hypothesize differential mechanisms within these peptidergic systems: that increased GnRH-1 immunoreactivity during the nonbreeding season reflects increased accumulation with reduced release; that increased kisspeptin immunoreactivity during the breeding season reflects increased synthesis with increased release.

Original languageEnglish
JournalJournal of Comparative Neurology
Early online date13 Jul 2018
DOIs
Publication statusE-pub ahead of print - 13 Jul 2018

Keywords

  • Afrotheria
  • anteroventral periventricular nucleus
  • arcuate nucleus
  • gonadotrophin-releasing hormone-1
  • kisspeptin
  • RRID:AB_2315026
  • RRID:AB_2631061
  • RRID:AB_572248
  • RRID:SCR_002865
  • RRID:SCR_003070
  • RRID:SCR_014199
  • seasonal reproduction

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