Department of Wildland Resources, Utah State University, Logan, UT 84322-5230, USA.
Theriogenology. 2009 Oct 1;72(6):773-83. doi: 10.1016/j.theriogenology.2009.05.012. Epub 2009 Jul 24.
Wild Canis species such as the coyote (C. latrans) express a suite of reproductive traits unusual among mammals, including perennial pair-bonds and paternal care of the young. Coyotes also are monestrous, and both sexes are fertile only in winter; thus, they depend upon social and physiologic synchrony for successful reproduction. To investigate the mutability of seasonal reproduction in coyotes, we attempted to evoke an out-of-season estrus in October using one of two short-acting gonadotropin-releasing hormone (GnRH) agents: (1) a GnRH analogue, deslorelin (6-D-tryptophan-9-(N-ethyl-L-prolinamide)-10-deglycinamide), 2.1mg pellet sc; or (2) gonadorelin, a GnRH (5-oxoPro-His-Trp-Ser-Tyr-Gly-Leu-Arg-Pro-GlyNH(2)) porcine hypothalamic extract, 2.0 microg/kg im once daily for 3 consecutive days. A transient increase in serum concentrations of estradiol and progesterone (1 and 2 wk, respectively) was detected after treatment with deslorelin but not gonadorelin. Also, socio-sexual behaviors reminiscent of winter mating (including courtship, mate-guarding, precoital mounts, and copulatory ties) were observed among the deslorelin group. During the subsequent breeding season (January and February), however, preovulatory courtship behavior and olfactory sampling appeared suppressed; emergence of mounts and copulations were delayed in both deslorelin and gonadorelin treatment groups. Furthermore, whereas 8 of 12 females treated in October ovulated and produced healthy litters in the spring, 4 naïve coyotes failed to copulate or become pregnant. Thus, perturbation of hormones prior to ovulation in species with complex mating behaviors may disrupt critical intrapair relationships, even if fertility is not impaired physiologically.
野生犬科物种，如郊狼（C. latrans），表现出一系列在哺乳动物中不常见的生殖特征，包括常年的配对关系和雄性对幼崽的照顾。郊狼也是单发情的，雌雄两性只有在冬季才具有生育能力；因此，它们依靠社会和生理同步来实现成功繁殖。为了研究郊狼季节性繁殖的可变性，我们试图在 10 月使用两种短期作用的促性腺激素释放激素（GnRH）制剂之一来引发非季节性发情：（1）一种 GnRH 类似物，地洛瑞林（6-D-色氨酸-9-（N-乙基-L-脯氨酰胺）-10-去甘氨酰胺），2.1mg 皮下植入；或（2）促性腺激素释放激素，一种 GnRH（5-氧代脯氨酸-组氨酸-色氨酸-丝氨酸-酪氨酸-甘氨酸-亮氨酸-精氨酸-脯氨酸-甘氨酸-NH2）猪下丘脑提取物，2.0μg/kg 肌肉注射，连续 3 天，每天一次。在用地洛瑞林治疗后，检测到血清雌二醇和孕酮浓度的短暂升高（分别为 1 周和 2 周），但用促性腺激素释放激素治疗则没有。此外，地洛瑞林组中观察到类似于冬季交配的社交性行为（包括求爱、伴侣保护、交配前交配和交配联系）。然而，在随后的繁殖季节（1 月和 2 月）中，发情前的求爱行为和嗅觉采样似乎受到抑制；地洛瑞林和促性腺激素释放激素治疗组的交配和交配出现延迟。此外，虽然 10 月接受治疗的 12 只雌性中有 8 只排卵并在春季产下健康的幼崽，但 4 只未接受治疗的郊狼未能交配或怀孕。因此，在具有复杂交配行为的物种中，在排卵前扰乱激素可能会破坏关键的配对关系，即使生理上不受损害。
