beta-adrenergic receptor blockade by propranolol enhances retention in a multitrial passive-avoidance procedure

The effect of beta -adrenergic receptor blockade on retention in a mildly a versive passive-avoidance procedure was investigated. Rats were given passi ve-avoidance training-1 trial per day for 4 days-and were administered sali ne, the centrally and peripherally acting beta -adrenergic blocker proprano lol (4 or 10 mg/kg ip), or the peripherally acting P-adrenergic blocker sot alol (4 or 10 mg/kg ip) immediately or 2 hr after the Ist trial. Enhanced r etention occurred only with the higher dose (10 mg/kg) of propranolol and o nly when it was administered immediately after training. The enhanced reten tion produced by propranolol is discussed in terms of opposing, regionally specific actions of beta -adrenergic receptor-mediated neural circuits on m odulation of memory.