Larivière K, Samia M, Lister A, Van Der Kraak G, Trudeau V L
Department of Biology, Centre for Advanced Research in Environmental Genomics, Canada.
Brain Res Mol Brain Res. 2005 Nov 18;141(1):1-9. doi: 10.1016/j.molbrainres.2005.06.005. Epub 2005 Oct 13.
GABA, the major inhibitory neurotransmitter of the vertebrate brain, has been shown to play an important role in vertebrate reproduction by regulating LH release and sexual behavior. We have studied the expression of the GABA-synthesizing enzyme, glutamic acid decarboxylase (GAD), in goldfish throughout the reproductive cycle in May (mature), November (early gonadal recrudescence) and February (late gonadal recrudescence) and in response to implanted sex steroids. Levels of GAD67 and GAD65 mRNA levels in the hypothalamus of both males and females were highest in the early stages of gonadal recrudescence. In the telencephalon, a different seasonal pattern of GAD expression was evident. The telencephalic expression GAD67, GAD65 and a novel isoform, GAD3, were highest in sexually mature fish in May. Five-day intraperitoneal implantation of gonad-intact fish with testosterone (T), estradiol (E2) or progesterone (P4) did not affect GAD expression in November and February. This is in contrast to results in May when sex differences in steroid responsiveness were evident. Progesterone decreased hypothalamic GAD67 and GAD65 in females and was without effect in males. All other treatments did not alter GAD67, GAD65 or GAD3 expression in the hypothalamus. Both T and P4 decreased GAD67 and GAD65 levels in the telencephalon of male goldfish but had no effect in females. Serum sex steroid levels in control and implanted mature males and females in May were similar so it is unlikely that sex differences in the GAD responses were a result of differences in serum sex steroid levels. These contrasting effects of sex steroids on males and females suggest important sex differences in the regulation of the GADs in sexually mature goldfish.
γ-氨基丁酸（GABA）是脊椎动物大脑中的主要抑制性神经递质，已被证明通过调节促黄体生成素（LH）释放和性行为在脊椎动物繁殖中发挥重要作用。我们研究了在五月（成熟）、十一月（性腺早期复壮）和二月（性腺晚期复壮）整个生殖周期以及对植入性类固醇的反应中，金鱼体内GABA合成酶谷氨酸脱羧酶（GAD）的表达情况。雄性和雌性金鱼下丘脑的GAD67和GAD65 mRNA水平在性腺复壮早期最高。在端脑，GAD表达呈现出不同的季节性模式。端脑GAD67、GAD65和一种新亚型GAD3的表达在五月性成熟的鱼类中最高。对性腺完整的鱼类进行为期五天的腹腔内植入睾酮（T）、雌二醇（E2）或孕酮（P4），在十一月和二月并未影响GAD表达。这与五月的结果形成对比，五月时类固醇反应的性别差异很明显。孕酮降低了雌性下丘脑的GAD67和GAD65，对雄性则无影响。所有其他处理均未改变下丘脑的GAD67、GAD65或GAD3表达。T和P4均降低了雄性金鱼端脑的GAD67和GAD65水平，但对雌性无影响。五月对照和植入类固醇的成熟雄性和雌性的血清性类固醇水平相似，因此GAD反应的性别差异不太可能是血清性类固醇水平差异的结果。性类固醇对雄性和雌性的这些不同作用表明，在性成熟金鱼中，GAD的调节存在重要的性别差异。
