Neuroethological analysis of memory retention in conditioned taste aversion.

静脉麻醉药如异丙酚可引起前行性和逆行性健忘症。在先前的研究中，这些麻醉药在条件刺激（CS）出现之前的应用不会影响条件味觉厌恶（CTA）的获得。另一方面，去甲肾上腺素能系统被认为对记忆保持起着重要作用。因此，我们研究了异丙酚在CS和非条件刺激（US）之间应用对CTA保留的影响。不同浓度的丙泊酚不影响CTA的获得。然而，CTA的保留被剂量依赖性地抑制。一种α 2受体阻滞剂育亨宾也显著损害了CTA的保留。这些结果表明，低浓度的异丙酚影响CTA记忆保留机制，包括α 2去甲肾上腺素能受体。在小鼠近交系C57BL/6中获得了类似的结果，表明小鼠在情绪学习和记忆系统中具有与大鼠相同的对异丙酚敏感的部位。我们试图确定大脑中异丙酚的接受部位，使用一种即时早期基因，cFos免疫反应性（Fos-IR）作为神经元激活的制造蛋白。在CTA获取1小时后经核α α灌注固定小鼠脑，并比较异丙酚注射组（异丙酚组）与生理盐水注射组在味觉第二中枢、臂旁核（PBN）、丘脑前核、杏仁核和大脑皮层味觉区（岛叶皮质）等脑区Fos-IR的变化。我们发现Fos-IR倾向于在杏仁核基底外侧增加，尽管在所有被检查的大脑区域没有显著差异。这些结果表明，杏仁核在CTAM的保留和获得中起重要作用。

Intravenous anesthetics such as propofol are known to induce antero- and retrograde amnesia. In previous works, these anesthetics have been reported not to affect the acquisition of conditioned taste aversion(CTA) by their application prior to the presentation of conditioned stimulus(CS). On the other hand, the noradrenergic system is thought to play an important role for the memory retention. Therefore, we examined the effect of propofol applied between CS and unconditioned stimulus(US) on retention of CTA. Propofol did not affect the acquisition of CTA in all concentrations examined. However, the retention of CTA was dose-dependently suppressed by them. An alpha2 blocker, yohimbine, also remarkably impaired the retention of CTA. These results suggest that low concentrations of propofol affect the CTA memory retention mechanism including alpha2 noradrenergic receptors. The similar results were obtained with mice from a mouse inbred strain, C57BL/6,suggesting that mice have a common site sensitive to propofol in the emotional learning and memory system to rats.We tried to identify the receptive site of propofol in the brain, using an immediately early gene, cFos immunoreactivity (Fos-IR) as a maker protein for neuronal activation. The mice brain was fixed by transcardial α α perfusion 1 hr after CTA acquisition and Fos-IR of a group injected with propofol (propofol group) was compared to that of a control group injected with physiological saline at several brain area including the secondary center of gustatory sense, parabrachial nucleus(PBN), the anterior nuclei of thalamus, the amygdala and the cerebral cortex gustatory area (insular cortex). We found that Fos-IR tend to increase in the basolateral amygdala, in spite of no significant difference in all the brain area examined. These results suggest that the amygdala plays important roles on the retention as well as the acquisition of CTAM.