A post-tetanic time window for the reinforcement of long-term potentiation by appetitive and aversive stimuli.

Current theories on the encoding and storage of information in the brain commonly suppose that a short-term memory is converted into a lasting one; thus, it becomes consolidated over time. Within a finite period after training, such a short-term memory can be reinforced by behavioral and humoral stimuli. We have found that, long-term potentiation (LTP), a likely candidate for a memory-encoding mechanism at the cellular level, displays similar features. LTP in the dentate gyrus of freely moving rats was reinforced after its induction by appetitive and aversive stimuli. The efficacy of these stimuli terminates about 1 h after tetanization, which may reflect the time constants of the mechanisms underlying the consolidation that takes place. The reinforcement by appetitive and aversive stimulation was blocked by the beta-adrenergic antagonist propranolol, implicating norepinephrine in the underlying cellular processes.