Abstract
Kisspeptin is a neuropeptide that governs the reproductive axis upstream to GnRH. We wanted to study whether kisspeptin modulates plasma LH and FSH levels and ovarian follicular dynamics in buffaloes and whether kisspeptin can be used for fixed time artificial insemination (FTAI). We carried out these studies in comparison with buserelin, a potent GnRH agonist. Kisspeptin dose-dependently increased plasma LH levels. However, the kisspeptin-induced increase in LH was short-lived as the peak reached in 15–30 min returned to basal values by 1–2 h. The kisspeptin-induced increase in LH level was less compared to buserelin-induced increase in LH level which sustained over time. Kisspeptin did not enhance FSH release while buserelin resulted in a gradual increase over time. LH response to repeated injections of kisspeptin was greater than that induced by buserelin. While buserelin induced an increase in the number of follicles, kisspeptin induced an increase in the growth rate of the follicle. In adult cycling animals, while both the drugs increased plasma LH levels, the increase was greater in buserelin group compared to kisspeptin group. In contrast to the findings in pre-pubertal animals, kisspeptin induced an increase in both the number as well as the size of follicles compared to buserelin. Our studies on oestrus synchronization, using either kisspeptin-PGF2α-kisspeptin protocol or buserelin-PGF2α-buserelin Ovsynch protocol on day 0, 7, and 9, respectively, revealed that kisspeptin increased the number of follicles at wave emergence and the diameter of dominant follicle after 2nd dose of drug, the oestrus response rate and duration of oestrus, compared to buserelin. However, conception rate was not significantly different among the groups. From our studies, it appears that Kp and Buserelin differentially modulate follicular dynamics depending on the reproductive age of the animals.However, studies in a larger herd are required to confirm whether kisspeptin can be used for oestrous synchronization in buffaloes.
Highlights
Kisspeptin is one of the controllers of hypothalamo-pituitarygonadal (HPG) axis upstream to gonadotropin releasing hormone (GnRH)
We report our findings on oestrus synchronization in buffaloes when kisspeptin is used instead of buserelin, a potent GnRH agonist
follicle stimulating hormone (FSH) was not significantly elevated upon kisspeptin, while buserelin IV increased FSH in a slow and sustained manner (IV: Basal vs. at 1.5 and 2 h, P < 0.05, RM ANOVA followed by multiple comparison tests; Figures 3C,D), similar to that of luteinizing hormone (LH) response
Summary
Kisspeptin is one of the controllers of hypothalamo-pituitarygonadal (HPG) axis upstream to gonadotropin releasing hormone (GnRH). Kisspeptin is expressed in the arcuate nucleus and rostral periventricular region in rats and in the arcuate nucleus and preoptic area in sheep [2, 3]. Apart from hypothalamus, expressionof Kiss gene and immunoreactivity of kisspeptin and its receptor, GPR54, have been reported in extra-hypothalamic tissues, such as ovaries, in rats and sheep [4]. GnRH or luteinizing hormone (LH) are being used to induce ovulation, via oestrus synchronization protocol, in subfertile buffaloes. The conception rate is only 50–55% in a synchronization protocol that uses GnRH and prostaglandin [5]. New therapeutic strategies aiming at increased conception rate and reduced fertility disorders are warranted. Studying the endocrine profile and follicular dynamics upon kisspeptin administration would be a key step toward kisspeptin-based therapeutic strategies
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