檢測抬高式T形迷津行為之焦慮源

Identification of Anxiogenic Stimuli for Behavioral Performance in the Elevated T-maze

在抬高式T形迷津，大白鼠可以很快習得滯留在有牆的封閉區而不冒然進入開放區的制約躲避行為，受試緊接著被置於開放區的一端時，它會立即表現出脫逃行為，由開放區迅速逃離前往封閉區。從過去研究利用臨床有效的抗焦慮症藥物的藥理檢驗結果，推測這型迷津的二種行為與不同型式的焦慮有關，但建構行為的動力機制迄今未曾被有系統的檢驗過。本研究藉操弄迷津平台的離地高度、不同型式的封牆，及開放區走道的加寬以檢驗引起焦慮的刺激源何在，結果顯示開放區的空曠訊息對受試的衝擊是主要的焦慮源所在，但來自高度訊息的衝擊不能完全被排除。另外一項實驗比較此迷津的兩種作業以先後不同的次序進行，結果顯示這個有關實驗步驟的操弄並不影響制約躲避行為與脫逃行為的反應，亦即先曝露於開放區的即刻經驗尚不足以影響制約躲避行為的習得歷程。藉由血清張力素類的抗焦慮藥物buspirone分別對這種迷津行為及自發性運動反應進行藥物劑量的藥理檢驗，此藥採較低劑量（0.3 mg/kg）注射可以明顯的減抑制約躲避行為的習得而不影響脫逃行為，而此抗焦慮的藥效無關乎此藥對自發性運動量的改變。本研究結果為此型迷津運用在心理藥理學探討焦慮的動物模式，提供了行為檢驗的信度與效度之相關證據。

In the elevated T-maze, a rat can rapidly acquire the conditioned avoidance behavior when remaining in the enclosed area instead of lingering in the open area. Immediately after avoidance conditioning, escape from the open area with a quick motion to enter into enclosed area appeared when the subject was placed at one end of the open area. Previous work examined the effects of anxiolytic drugs on elevated T-maze, the results suggest two types of anxiety disorder could be distinctly related to conditioned avoidance and escape. However, the mechanisms for those two behaviors in elevated T-maze remain unclear. The present study manipulated the height of maze plate, different forms of wall surrounding enclosed and/or open area, and the width of arms in open area to investigate the anxiogenic stimuli for elevated T-maze. Results indicated that the openness in the open area is the predominant factor for anxiogenesis and, in addition, the impact from height perceived by subject may also be involved. In another experiment the procedures of the two tasks in the elevated T-maze were re-examined and the results excluded the putative confounding effect as derived from different sequences in testing behaviors on this maze. The dose effects of buspirone, known as a serotoninergic anxiolytic drug, were evaluated on elevated T-maze and locomotor activity separately. Buspirone injected with low dose (0.3 mg/kg) significantly reduced the conditioned avoidance latency without affecting the escape latency in elevated T-maze. That locomotor activity was not altered by buspirone given at this dose suggests the irrelevance of anxiolytic effect observed from T-maze with locomotion under drug treatment. Together, results of this study provided evidence in regarding the reliability and validity for using elevated T-maze as an animal model of anxiety in psychopharmacology.