Decrements in avoidance behavior following mammillothalamic tractotomy in rats and subsequent recovery with d-amphetamine.

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Abstract
Rats in Experiment 1 showed significant decrements in relearning a shuttlebox conditioned avoidance response (CAR) following partial bilateral and unilateral mammillothalamic tract (MTT) lesions, thus confirming earlier work on cats. In Experiment 2, 2 rats with an almost complete loss of the CAR following bilateral MTT lesions showed marked recovery of the CAR following ip injections of 2 mg/kg of d-amphetamine. Poorly performing unlesioned Ss showed a similar improvement with d-amphetamine. CAR returned to predrug levels in all Ss immediately following withdrawal of d-amphetamine. That all Ss given d-amphetamine showed substantial reductions in freezing behavior several trials before improvement in CAR was taken as evidence that freezing may effect level of avoidance responding.