Foy Michael R, Foy Judith G
Department of Psychology, Loyola Marymount University, Los Angeles, CA 90045, USA.
Integr Physiol Behav Sci. 2003 Jul-Sep;38(3):203-13. doi: 10.1007/BF02688854.
Conditioned taste aversion (CTA) learning is an adaptive, robust, well-established learning and memory paradigm. Strong taste aversions develop to the conditioned stimulus (CS = saccharin) despite long delays between exposure to the CS and unconditioned stimulus (US = LiCl). Rats display a sexually dimorphic pattern of long-delay CTA learning (Foy et al., 1996). The present study examines whether this sex difference is a result of activational or organizational hormone action, because here we implanted gonadectomized rats with their normal hormone replacements, or with opposing hormones prior to testing in a 4-hr delayed CTA learning task. We found that gonadally intact male rats displayed a more robust CTA response than intact female rats. Gonadectomy essentially eliminated this sex difference; gonadectomized males and gonadectomized females displayed similar CTA responses. In gonadectomized rats, when their normal sex hormones were replaced with implanted hormone pellets, the sex difference in CTA learning was reinstated. In contrast, when gonadectomized rats were implanted with opposing hormones, the sex difference was reversed. Gonadectomized female rats implanted with 5alpha-DHT pellets (metabolite of testosterone) displayed a stronger CTA response compared to gonadectomized males implanted with 17beta-estradiol pellets. Regardless of the original developmental hormonal environment, our study suggests that an activational manipulation of circulating hormones serves to significantly influence long-delay CTA learning in rats.
条件性味觉厌恶（CTA）学习是一种适应性强、稳固且成熟的学习与记忆范式。尽管条件刺激（CS = 糖精）与非条件刺激（US = 氯化锂）之间存在长时间延迟，但对条件刺激仍会形成强烈的味觉厌恶。大鼠在长延迟CTA学习中表现出性别二态性模式（Foy等人，1996年）。本研究考察这种性别差异是激活性激素作用还是组织性激素作用的结果，因为在此我们给去势大鼠植入其正常激素替代物，或在进行4小时延迟CTA学习任务测试前植入相反的激素。我们发现性腺完整的雄性大鼠比完整的雌性大鼠表现出更强健的CTA反应。去势基本消除了这种性别差异；去势雄性大鼠和去势雌性大鼠表现出相似的CTA反应。在去势大鼠中，当用植入的激素丸剂替代其正常性激素时，CTA学习中的性别差异得以恢复。相反，当给去势大鼠植入相反的激素时，性别差异则发生逆转。植入5α - 双氢睾酮丸剂（睾酮的代谢产物）的去势雌性大鼠比植入17β - 雌二醇丸剂的去势雄性大鼠表现出更强的CTA反应。无论原始发育激素环境如何，我们的研究表明对循环激素的激活操作会显著影响大鼠的长延迟CTA学习。
