Effects of Kisspeptin on rabbit ovulation: a comprehensive study of ovulatory, endocrine and histological response

Mammalian reproductive function is regulated by hypothalamic neurons that secrete Kisspeptin (Kp), a neuropeptide that stimulates gonadotropin-releasing hormone (GnRH) secretion, triggering pituitary gonadotrophins (LH and FSH) and gonadal steroids. This study evaluated the effect of Kisspeptin-10 (Kp10) on ovulation induction in rabbits, comparing its efficacy with that of the GnRH analogue gonadorelin. Multiparous New Zealand White × California does were assigned to three groups: control group (0.5 % saline solution, i.v.), GnRH group (20 μg gonadorelin, i.m.), and Kp10 group (250 μg Kp10, i.v.). Kp10 induced ovulation in 87.5 % of does, matching the response observed in the GnRH group, with a comparable number of corpora lutea (CL) per ovulated doe (12.9 ± 1.4 vs 14.6 ± 1.4 CL/doe, respectively). On day 7, plasma progesterone (P4) was significantly higher in ovulated GnRH-treated does than in Kp10-treated ones (25.12 ± 4.17 vs 9.47 ± 4.17 ng/mL; p < 0.0211), while non-ovulated controls exhibited minimal P4 concentrations (0.86 ± 0.12 ng/mL). Plasma estradiol (E2) levels showed no significant differences across days or groups, with mean values of 32.74 ± 4.33 pg/mL on day 0 and 37.27 ± 5.49 pg/mL on day 7, respectively. Histological analysis confirmed that Kp10 promoted preovulatory follicle development and CL formation, mirroring GnRH effects. Additionally, Kp10 enhanced angiogenesis, indicated by increased vascular endothelial growth factor (VEGF) expression in more developed follicles and CL. These results suggest that Kp10 could be an alternative to GnRH for ovulation induction in rabbits, although further studies are needed to explore optimal analogues, doses, and administration routes.