Propranolol Degrades Memory Reconsolidation in Conditions of Single and Multiple Combinations of Tones with Pain

The effects of propranolol on the state of memory after its reactivation (in the reconsolidation phase) were studied using two approaches – classical Pavlovian conditioning and acquisition of a two-way escape reaction. The difference between them was that in the first case, the tone was combined with painful electrocutaneous stimulation just once, while in the latter it was combined multiple times. Reminding in the former case was induced by placing the animals in the same context in which primary training was performed, while in the latter the number of combinations of the conditioned and unconditioned stimuli was the same as that used on the first day of training. Administration of propranolol decreased the duration of freezing episodes by 25% compared with the baseline level in classical conditioning and led to essentially complete loss of memory and complete regression of the two-way escape reaction. It is suggested that the effects of blockade of the noradrenergic system on loss of memory in the reconsolidation stage in these learning models have different mechanisms.

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