NOVEL CONTEXT EXPOSURE ENHANCES OBJECT RECOGNITION MEMORY: ASSESSING INVOLVEMENT OF NOREPINEPHRINE NEUROTRANSMISSION

Long-term memories are encoded within the hippocampus, but some are quickly forgotten. Brief exposure of mice to a novel context following encoding of object memory significantly enhances consolidation of the object memory. The memory-enhancing effect of post-training novelty may rely on locus coeruleus tyrosine-hydroxylase expressing neurons which co-release norepinephrine and dopamine in the hippocampus. To test the contribution of norepinephrine to this novelty effect, mice received propranolol, a synthetic beta-adrenergic receptor antagonist (10 mg/kg), to block norepinephrine or 0.9% saline as a control post-training. Pre-novel context exposure and object memory was tested 24 hr later. Results revealed that propranolol did not block the memory enhancing effect of post-training novel context exposure. Further, the memory performance of the propranolol-treated mice was comparable to that of saline-treated mice. These findings support the view that enhanced consolidation of object memory brought about by post-training novel context exposure is not dependent upon norepinephrine neurotransmission.