Bucherelli C, Tassoni G
Dipartimento di Scienze Fisiologiche, Firenze, Italy.
Behav Brain Res. 1992 Oct 31;51(1):61-5. doi: 10.1016/s0166-4328(05)80312-2.
Previous studies have shown that in rats the acquisition of a step-through passive avoidance reaction (PAR) in the light-dark box apparatus is disrupted by tetrodotoxin (TTX) inactivation of the parabrachial nuclei (PBN) 24 but not 48 h after the acquisition trial. The present experiment shows that TTX induces retrograde amnesia even when applied to the PBN 48 h after PAR acquisition only if it is preceded by a 30-min confinement (extinction) or by a footshock (retraining) in the dark compartment. These stimuli, independently of their sign, induce quantitatively comparable TTX disrupting effects. This happens notwithstanding the fact that these stimuli are too weak to modify PAR under control conditions. This paradoxical finding suggests that engram vulnerability may not be a simple inverse function of its recency but that it may reflect a reactivation of the neural circuits involved in memory trace formation. Consolidated engrams become again vulnerable only when contextual cue stimuli are presented shortly before the application of the disrupting procedure.
先前的研究表明，在大鼠中，在明暗箱装置中获得穿梭式被动回避反应（PAR）后24小时，臂旁核（PBN）被河豚毒素（TTX）灭活会干扰该反应，但在获得试验后48小时则不会。本实验表明，仅当在暗室中先进行30分钟的禁闭（消退）或电击（再训练）后，TTX即使在PAR获得后48小时应用于PBN，也会诱导逆行性遗忘。这些刺激，无论其信号如何，都会诱导出数量上可比的TTX干扰效应。尽管这些刺激在对照条件下太弱而无法改变PAR，但仍会出现这种情况。这一矛盾的发现表明，记忆痕迹的脆弱性可能不是其新近性的简单反函数，而是可能反映了参与记忆痕迹形成的神经回路的重新激活。只有在应用干扰程序前不久呈现情境线索刺激时，巩固的记忆痕迹才会再次变得脆弱。
