Possible peripheral adrenergic and central dopaminergic influences in memory consolidation.

The posttrial i.p. administration of clonidine (0.1 mg/kg) or haloperidol (0.5 mg/kg) to rats trained on a shuttle avoidance paradigm resulted in lower retention of the task in a retest session carried out 7 days later, compared to animals which received posttrial saline injections. The effect of clonidine was antagonized by either phenoxybenzamine (10 mg/kg) or phentolamine (10 mg/kg) i.p., and that of haloperidol was antagonized by 4, but not by 0.5 mg/kg of apomorphine i.p. Neither apomorphine, nor phentolamine or phenoxybenzamine had any effect on their own. The data suggest that memory consolidation of two-way avoidance may be influenced by presumably peripheral adrenergic mechanisms and by presumably central dopaminergic mechanisms.