Brain noradrenergic responses to training and to amnestic frontal cortex stimulation.

Rats were trained in a one-trial inhibitory (passive) avoidance task prior to receiving supraseizure electrical stimulation of frontal cortex, a treatment that results in amnesia. Forebrain and brain stem norepinephrine (NE) concentrations decreased by 23% 10 min after footshock training. Posttraining frontal cortex stimulation resulted in a potentiation of the forebrain NE response (to 31-33% below control values) and in attenuation of the brainstem response (0-5% lower than control values). These results are consistent with previous findings that indicate that good retention performance is predicted by training and treatment conditions that result in approximately a 20% decrease in brain NE content as measured 10 min after training; deviations from this optimal level, presumably reflecting more or less NE release, predict poor retention in comparably trained and treated rats. Thus, memory storage processing appears to be sensitive to many manipulations that alter the endogenous posttraining brain NE response to footshock.