Caldwell H K, Albers H E
Department of Biology, Center for Behavioral Neuroscience, Georgia State University, Atlanta, GA 30303, USA.
J Neuroendocrinol. 2003 Oct;15(10):971-7. doi: 10.1046/j.1365-2826.2003.01086.x.
In Syrian hamsters, socially relevant information is communicated with a form of scent marking known as flank marking. There is substantial evidence that arginine-vasopressin acting on V1a vasopressin receptors (V1aR) in the medial preoptic-anterior hypothalamic continuum (MPOA-AH) regulates the expression of flank marking. Previous studies have shown that the expression of flank marking is also influenced by the circulating concentrations of gonadal hormones. In hamsters housed in long 'summer-like' photoperiods (i.e. >12.5 h of light/day), castration reduces flank marking and administration of testosterone restores precastration levels of flank marking. When exposed to short 'winter-like' photoperiods (i.e. <12.5 h of light/day), hamsters undergo gonadal regression and the circulating levels of testosterone decline. Surprisingly, flank marking induced during social encounters is not reduced in hamsters exposed to short photoperiods despite the low circulating concentrations of testosterone. In the present study, it was hypothesized that reductions in testosterone, caused by exposure to short photoperiod, would not reduce the ability of vasopressin to stimulate flank marking by its actions in the MPOA-AH. The amount of flank marking induced by vasopressin injected into the MPOA-AH did not significantly differ between hamsters housed in long and short photoperiods; however, short photoperiod-exposed males had significantly less V1aR binding in the MPOA than long photoperiod-exposed males. These results support the hypothesis that the sensitivity of the MPOA-AH to vasopressin is not reduced in short photoperiod-exposed males, despite decreases in serum testosterone. However, by contrast to our predictions, short photoperiod-exposed males have significantly reduced V1aR binding in the MPOA-AH compared to long photoperiod-exposed males.
在叙利亚仓鼠中，与社会行为相关的信息通过一种名为胁腹标记的气味标记形式进行传递。有大量证据表明，作用于内侧视前区 - 下丘脑前部连续区域（MPOA - AH）中V1a血管加压素受体（V1aR）的精氨酸血管加压素调节胁腹标记的表达。先前的研究表明，胁腹标记的表达也受性腺激素循环浓度的影响。在处于长“类似夏季”光周期（即每天光照>12.5小时）饲养的仓鼠中，去势会减少胁腹标记，而注射睾酮可恢复去势前的胁腹标记水平。当暴露于短“类似冬季”光周期（即每天光照<12.5小时）时，仓鼠会出现性腺退化，睾酮的循环水平下降。令人惊讶的是，尽管睾酮的循环浓度较低，但在短光周期下暴露的仓鼠在社交互动中引发的胁腹标记并未减少。在本研究中，研究人员提出假设，即暴露于短光周期导致的睾酮减少不会降低血管加压素通过其在MPOA - AH中的作用刺激胁腹标记的能力。向MPOA - AH注射血管加压素诱导的胁腹标记量在长光周期和短光周期饲养的仓鼠之间没有显著差异；然而，与长光周期暴露的雄性相比，短光周期暴露的雄性在MPOA中的V1aR结合显著减少。这些结果支持了这样的假设，即尽管血清睾酮减少，但在短光周期暴露的雄性中，MPOA - AH对血管加压素的敏感性并未降低。然而，与我们的预测相反，与长光周期暴露的雄性相比，短光周期暴露的雄性在MPOA - AH中的V1aR结合显著减少。
