Allen Timothy A, Narayanan Nandakumar S, Kholodar-Smith Dianna B, Zhao Yanjun, Laubach Mark, Brown Thomas H
Department of Psychology, Yale University, 2 Hillhouse Avenue, New Haven, CT 06520, United States.
J Neurosci Methods. 2008 Jun 15;171(1):30-8. doi: 10.1016/j.jneumeth.2008.01.033. Epub 2008 Mar 10.
Muscimol is a GABA A-agonist that causes rapid and reversible suppression of neurophysiological activity. Interpretations of the effects of muscimol infusions into the brain have been limited because of uncertainty about spread of the drug around the injection site. To solve this problem, the present study explored the use of a fluorophore-conjugated muscimol molecule (FCM). Whole-cell recordings from horizontal brain slices demonstrated that bath-applied FCM acts like muscimol in reversibly suppressing excitatory synaptic transmission. Two types of in vivo experiments demonstrated that the behavioral effects of FCM infusion are similar to the behavioral effects of muscimol infusion. FCM infusion into the rat amygdala before fear conditioning impaired both cued and contextual freezing, which were tested 24 or 48 h later. Normal fear conditioning occurred when these same rats were subsequently given phosphate-buffered saline infusions. FCM infusion into the dorsomedial prefrontal cortex impaired accuracy during a delayed-response task. Histological analysis showed that the region of fluorescence was restricted to 0.5-1mm from the injection site. Myelinated fiber tracts acted as diffusional barriers, thereby shaping the overall spread of fluorescence. The results suggest that FCM is indeed useful for exploring the function of small brain regions.
蝇蕈醇是一种γ-氨基丁酸A型（GABA A）激动剂，可快速且可逆地抑制神经生理活动。由于药物在注射部位周围扩散的不确定性，对向大脑注射蝇蕈醇的效果的解释一直有限。为了解决这个问题，本研究探索了使用一种荧光团偶联的蝇蕈醇分子（FCM）。对水平脑片进行的全细胞记录表明，通过浴槽施加的FCM在可逆地抑制兴奋性突触传递方面的作用与蝇蕈醇相似。两种体内实验表明，注射FCM的行为效应与注射蝇蕈醇的行为效应相似。在恐惧条件反射前向大鼠杏仁核注射FCM会损害线索性和情境性僵立反应，在24或48小时后对这些反应进行测试。当随后给这些相同的大鼠注射磷酸盐缓冲盐水时，出现了正常的恐惧条件反射。在延迟反应任务期间，向背内侧前额叶皮质注射FCM会损害准确性。组织学分析表明，荧光区域局限于距注射部位0.5 - 1毫米处。有髓纤维束起到了扩散屏障的作用，从而塑造了荧光的整体扩散。结果表明，FCM确实有助于探索小脑区域的功能。
