This experiment examined the possible role of the sympathetic-adrenal medullary system in modulating memory processing. Rats were trained in a one-trial inhibitory (passive) avoidance task. Following training, some animals received frontal cortex stimulation at an intensity (5 mA) that produces brain seizure and retrograde amnesia. Plasma samples taken at intervals up to 40 min after training and treatment were analyzed for epinephrine and norepinephrine concentration. The results indicate that a training footshock elicits a large transient increase in the plasma concentrations of both amines. Frontal cortex stimulation administered 5 see after training did not increase the initial response although the treatment may have prolonged the time to return to basal values. These findings suggest that levels of catecholamines in plasma are increased by these training procedures and therefore have the potential to promote memory processing. However, the amnesia produced by frontal cortex stimulation does not appear likely to be mediated by these peripheral systems.
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