Analysis of gonadotrophin-releasing hormone-1 and kisspeptin neuronal systems in the nonphotoregulated seasonally breeding eastern rock elephant-shrew (Elephantulus myurus).
J Comp Neurol
; 526(15): 2388-2405, 2018 10 15.
Article
in En
| MEDLINE
| ID: mdl-30004584
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.
Key words
Full text:
1
Collection:
01-internacional
Database:
MEDLINE
Main subject:
Seasons
/
Sexual Behavior, Animal
/
Shrews
/
Gonadotropin-Releasing Hormone
/
Kisspeptins
Limits:
Animals
Language:
En
Journal:
J Comp Neurol
Year:
2018
Document type:
Article
Affiliation country:
South Africa