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.