CONCURRENT MUSCARINIC AND BETA-ADRENERGIC-BLOCKADE IN RATS IMPAIRS PLACE-LEARNING IN A WATER MAZE AND RETENTION OF INHIBITORY AVOIDANCE

These experiments examined the effects of separate and concurrent muscarinic cholinergic and β-adrenergic blockade on inhibitory (passive) avoidance performance and spatial learning in the Morris water maze. Pretraining systemic administration of either scopolamine (0.3 or 1.0 mg/kg) or propranolol (3.0 or 10.0 mg/kg) had no significant effect on one-day retention of step-through inhibitory avoidance training. Similarly, pretraining administration of either 0.3 mg/kg scopolamine or 10 mg/kg propanolol did not affect spatial learning in the Morris water maze. However, combined administration of scopolamine and 10.0 mg/kg of propranolol impaired performance on these tasks. These findings further support a role for interactions between norepinephrine and acetylcholine in the modulation of learning and memory and implicate the participation of β-adrenergic mechanisms in this interaction. Because cholinergic and noradrenergic deterioration is found in aging and Alzheimer's disease, these results also have implications regarding the role of age-related noradrenergic and cholinergic dysfunction in cognitive decline. © 1990.