正腎上腺素與腦啡在大白鼠杏仁核內之交互作用 在記憶形成過程中的角色

Abstract

在記憶形成的過程中，杏仁核扮演了非常重要的角色。本論文以大白鼠為實驗動物，利用三種方法探討杏仁核中正腎上腺素系統與類鴉片系統在記憶形成過程中的交互作用。在單向被動式逃避學習實驗中，訓練後直接將正腎上線素注射到杏仁核中，會產生倒U型劑量反應，且0.25μg的正腎上腺素可顯著的促進記憶；而注射0.1ng的Met-enkephalin則會顯著的抑制記憶。利用免疫組織化學染色的方法，在杏仁核的連續切片分別以多巴胺β羥化酵素及 Met-enkephalin的初級抗體進行染色，發現在杏仁核的中央核與基內核中，同時具有可分泌正腎上腺素的神經纖維與分泌Met-enkephalin的神經元和神經纖維的分佈。而在活體微透析的實驗當中，Met-enkephalin 1μg/ml與10μg/ml兩個劑量均會顯著抑制杏仁核中正腎上腺素的釋放。綜合以上的實驗結果，顯示Met-enkephalin應是藉由抑制杏仁核內正腎上腺素的釋放，而達到其抑制記憶的效果。

The present study investigated the interactions of norepinephrine (NE) and Met-enkephalin in the amygdala on memory process in rats. Post-training administration of NE (0.5μg,0.25μg,1.25μg) improved the retention performance of a passive avoidance learning task in rats and exhibited an inverted U-shaped dose-response curve with NE at the dose of 0.25μg significantly enhanced the retention performance. On the other hand, post-training administration of Met-enkephalin (0.1 ng) impaired retention performance. The co-distribution of noradrenergic and Met-enkephalinergic neurons or fibers in the amygdala was studied by using immunohistochemistry against dopamine-β-hydroxylase (DBH) and Met-enkephalin. Noradrenergic fibers were found almost in all nuclei of the amygdala. Met-enkephalinergic fibers were found only in the central and basomedial nuclei, and the neurons were distributed in the central nucleus. By investigating the immunoreactivities of DBH and Met-enkephalin in series dissection stained separately, we confirmed that the noradrenergic and Met-enkephalinergic neurons or fibers codistributed in the central and basomedial nuclei in the amygdala. Using the in vivo microdialysis assay coupled with electrochemical detection, we have found that Met-enkephalin (1μg/ml and 10μg/ml) significantly inhibited NE release from the amygdala. These results together support our hypothesis that Met-enkephalin may impair retention through inhibiting NE release in the amygdala.