PA-learning in young rats with dorsal hippocampal- and hippocampo-entorhinal atropine.

Twenty-one-day-old rats injected with atropine into dorsal hippocampus and trained on a white-black step-through passive avoidance task, did not perform differently from their controls in acquisition or extinction. In contrast, when atropine was administered into the ventral hippocampo-entorhinal area, the animals displayed a passive avoidance deficit. The results support the finding that the posteroventral but not the anterodorsal part of the hippocampal complex is implicated in passive avoidance learning and suggest a cholinergic mediation of this effect.