Inhibition of catecholamine biosynthesis and memory processes.

Rats injected with 60 mg/kg of alpha-methyl tyrosine (alpha-MT) immediately after a training in a shuttle box impaired retention of conditioned avoidance response (CAR). DL-Dopa (200 mg/kg) administered 5, 30, 60, and 120 min after alpha-MT treatment counteracted the depressive effect of this drug during the retention test; at longer times it was ineffective. Post-trial injections of 600 mg/kg of diethyldithiocarbamate (DDC) impaired retention of CAR; at a lower dose (300 mg/kg) it had no effect. Administration of alpha-MT (60 mg/kg) immediately after passive avoidance training lowered memory in females but not in males. These results suggest that noradrenaline (NA) is required for memory consolidation processes for about 2 h after training.