Effect of Heat Stress on the Expression of GABA Receptor mRNA in the HPG Axis of Wenchang Chickens

We investigated the effect of heat stress (HS) on the expression of the GABA receptor in the hypothalamic-pituitary-gonadal (HPG) axis of Wenchang chickens. Real-time quantitative RT-PCR (qRT-PCR) was used to quantify the GABA receptor mRNA levels along the HPG axis of chickens under HS (40 +/- 0.5 degrees C) for 1-6 weeks. Our results showed that the expression of GABA(A) and GABA(B) receptor at the mRNAs levels in the tissues of HPG axis exhibited fluctuation and variability. After HS, the mRNA level of GABA A receptor was significantly reduced in the hypothalamus of 1-week-old and in the pituitary of 3-week-old chickens, but significantly increased in the pituitary of 1-, 4-, and 5-week-old chickens. The GABA B receptor mRNA level significantly declined in the hypothalamus of 1-week-old and in the pituitary of 3-week-old chickens, but was significantly upregulated in the pituitary and testis of 1- and 2-week-old chickens. At other time points, the expressions of GABA A receptor and GABA B receptor showed no significant differences compared with control group. These results indicated that the levels of GABA A receptor and GABA B receptor mRNAs varied in different tissues of the HPG axis in chickens of different ages, displaying temporal and spatial variations. GABA receptor behaved as a positively-regulated gene by HS, i.e., its mRNA was increased by HS; similarly, it was a negatively-regulated gene by HS, when its expression was reduced by HS.

我们研究了热应激（HS）对文昌鸡下丘脑 - 垂体 - 性腺（HPG）轴中γ-氨基丁酸（GABA）受体表达的影响。采用实时定量逆转录聚合酶链反应（qRT - PCR）对在热应激（40 ± 0.5℃）条件下1 - 6周的鸡的HPG轴上的GABA受体mRNA水平进行定量。我们的结果显示，HPG轴组织中GABA（A）和GABA（B）受体在mRNA水平的表达呈现波动和变化。热应激后，1周龄鸡的下丘脑和3周龄鸡的垂体中GABA A受体的mRNA水平显著降低，但在1周龄、4周龄和5周龄鸡的垂体中显著升高。1周龄鸡的下丘脑和3周龄鸡的垂体中GABA B受体mRNA水平显著下降，但在1周龄和2周龄鸡的垂体和睾丸中显著上调。在其他时间点，与对照组相比，GABA A受体和GABA B受体的表达没有显著差异。这些结果表明，不同年龄鸡的HPG轴不同组织中GABA A受体和GABA B受体mRNA水平存在差异，表现出时空变化。GABA受体作为一个受热应激正调控的基因，即其mRNA在热应激下增加；同样，它也是一个受热应激负调控的基因，当它的表达在热应激下降低时。