Modulation of kisspeptin system could be beneficial to treat human infertility as well as to manage reproduction in domestic animals. We developed a series of kisspeptin analogs with improved pharmacological features. The lead compound, C6, triggers fertile ovulation in ewes in both breeding and non-breeding seasons. In addition daily injection of C6 (5X0.15 nmol) in prepubertal female mice from post-natal day 26 to 30 significantly advanced puberty. In this experimental setting following 5 daily injection, C6 effect on LH secretion was reduced suggesting a possible desensitization. Desensitization of gonadotrophe cells by continuous stimulation is a feature utilized to treat some hormone dependent cancers such as prostate cancer. Therefore, for field and therapeutic applications it is of paramount importance to identify the dosing regimen necessary to obtained continuous stimulation versus inhibition. We performed an initial experiment in adult mice ovariectomized (OVX) or OVX and replaced with estradiol (+E) to control for E feedback. In OVX+E mice daily injections of C6 (0.1 or 0.4 nmol/mouse ip) for 4 days produced no evident tachyphylaxis on LH plasma concentration increase. In the OVX mice the basal LH level was already high and C6 injection had minimal if any effect on LH plasma concentration. In both OVX and OVX+E mice, administration of GnRH at the end of the experiment induced a robust LH increase. To evaluate possible difference in species sensibility to repeated treatment we performed a similar experiment in OVX+E ewes. Intramuscular C6 injections were performed at 12 or 24-hour intervals (15 nmol/ewe/injection; 6 injections/ewe for the 12 hours and 4 injections/ewe for the 24 hours dosing regimen). Regardless to dosing regimen, the first injection induced an LH increase. However, subsequent injections had modest or no effect on LH plasma concentration. Injection of GnRH (5 μg) at the end of the 12 hours dosing regimen significantly increased LH. Ongoing experiments aim at evaluating the effect of injections every 36 or 48 hours to establish the minimal interval required to obtain repeated stimulation. These results suggest two main conclusions: i) under our experimental conditions the capacity for increased GnRH secretion is the potential limiting requirement for efficacious repeated C6 treatments; ii) a differential sensitivity to repeated treatment exists between species. Identification of the limiting conditions for sustained LH increase or desensitization will provide relevant information for developing field and therapeutic applications but caution should be used in translating information from one species to another.