The influence of galanin receptor agonist during the seasonal recrudescence and nonbreeding phases of the ovarian cycle in the gekkonid lizard Hemidactylus frenatus.

Galanin (GAL), a neuropeptide produced in both the central and peripheral nervous systems, is implicated in various physiological processes, including reproduction in vertebrates. Yet, the role of GAL is not understood in reptilian reproduction. This study aimed to investigate the impact of the galanin receptor agonist (GALR-A) on the reproductive axis during both the breeding and non-breeding phases of the ovarian cycle in the gecko Hemidactylus frenatus. During the recrudescence phase, administration of either a low (0.2 μg) or high dose (2 μg) of GALR-A did not affect either the follicular development up to stage IV (early vitellogenic) or gonadotropin-releasing hormone (GnRH) immunoreactivity in the median eminence (ME) and pars distalis of the pituitary gland (PD). However, stage V (late vitellogenic) follicles were absent in the ovary, in contrast to their appearance in experimental controls. In the regression phase, follicle-stimulating hormone (FSH) treatment led to the development of stage IV and V follicles, whereas treatment with a combination of 2 μg GALR-A and FSH did not stimulate the development of these follicles. In addition, in vitro treatment with GALR-A significantly reduced ovarian estradiol levels. Overall, these results suggest that GALR-A treatment disrupts the seasonal recrudescence potentially by interfering with the steroidogenesis and growth of vitellogenic follicles at advanced stages directly at the ovarian level in the gecko.