It is well established that acute food restriction (FR) has a suppressive effect on the reproductive system that may be mediated through attenuating the kisspeptin/GPR54 signaling in the hypothalamus. Kisspeptin neurons have been shown to express the dopamine D₂ receptor (D2R). The aim of the present study was to investigate the effect of chronic food restriction and/or antagonism of D2R by sulpiride on testosterone release and kisspeptin/GPR54 signaling in male rats. Sixty-six male Wistar rats, weighing-200 ± 20 g, were divided into seven groups including control, sham, 25%FR, 50%FR, 75%FR, sulpiride (50 µg/rat i.c.v., once at the end of treatment), 75%FR + sulpiride. FR was applied for 21 days. At the end, the mean serum testosterone level and the hypothalamic mRNAs expression of KiSS1, GPR54, D2R, and dopamine concentration were evaluated. The results demonstrated that the testosterone level significantly decreased in 50% and 75% food-restricted animals, and in sulpiride group, compared to control rats (P < 0.05). Injection of sulpiride to 75% food-restricted animals reduced the testosterone levels compared to all other groups (P < 0.05). Also, chronic 75%-FR significantly increased kisspeptin mRNA, dopamine concentration, but decreased D2R-mRNA (P < 0.05), and non-significantly decreased the GPR54mRNA (P > 0.05) compared to the control. Sulpiride injection to 75% food-restricted animals significantly decreased kisspeptin mRNA and increased dopamine concentration (P < 0.05), but had no significant effect on GPR54 or D2R-mRNAs expression, compared to 75% food-restricted group. In conclusion, we suggest that chronic food restriction decreases the testosterone release and then increases the kisspeptin/GPR54 signaling, and that the involvement of dopamine D₂ receptor in these effects.

众所周知，急性食物限制 (FR) 对生殖系统有抑制作用，这可能是通过减弱下丘脑中的 Kisspeptin/GPR54 信号传导来介导的。Kisspeptin 神经元已被证明表达多巴胺 D ₂受体（D2R）。本研究的目的是研究慢性食物限制和/或舒必利对 D2R 的拮抗作用对雄性大鼠睾酮释放和 Kisspeptin/GPR54 信号传导的影响。66 只雄性 Wistar 大鼠，体重 200 ± 20 g，分为七组，包括对照、假手术、25%FR、50%FR、75%FR、舒必利（50 µg/大鼠 icv，治疗结束时一次), 75%FR + 舒必利。FR应用了21天。最后，评估了平均血清睾酮水平和 KiSS1、GPR54、D2R 和多巴胺浓度的下丘脑 mRNA 表达。结果表明，与对照组相比，50%和75%禁食动物以及舒必利组的睾酮水平显着降低（P < 0.05)。与所有其他组相比，向 75% 禁食动物注射舒必利可降低睾酮水平（P  < 0.05）。此外，与对照相比，慢性 75%-FR 显着增加了 Kisspeptin mRNA、多巴胺浓度，但降低了 D2R-mRNA ( P  < 0.05)，并且非显着降低了 GPR54 mRNA ( P  > 0.05)。向 75% 禁食动物注射舒必利可显着降低 Kisspeptin mRNA 并增加多巴胺浓度（P < 0.05)，但与 75% 食物限制组相比，对 GPR54 或 D2R-mRNA 的表达没有显着影响。总之，我们建议长期饮食限制会降低睾酮释放，然后增加 Kisspeptin/GPR54 信号传导，以及多巴胺 D ₂受体参与这些作用。