Effects of alpha methyl-para-tyrosine on the recall of a passive avoidance response.

Treatment with alpha methyl-para-tyrosine 4 hr before training on a passive avoidance task altered recall in mice tested 24 hr after training. The observed alterations were dependent on the intensity of the footshock used during training. Retention of the avoidance habit was reduced by drug treatment when a footshock of 1.6 milliamperes (mA) was employed, while retention by drug-treated mice was enhanced when a footshock of 0.16 mA was used. No significant differences in retention were noted when a footshock of 0.8 mA or no footshock was employed. These results could not be explained on the basis of drug-induced changes in activity or sensitivity to footshock, of to state-dependent learning.