REVERSIBLE LESIONS OF THE NUCLEUS OF THE SOLITARY TRACT ATTENUATE THEMEMORY-MODULATING EFFECTS OF POSTTRAINING EPINEPHRINE

Rats implanted with cannula tips placed above the nucleus of the solit ary tract (NTS) were trained to obtain food pellets placed in 2 arms o f a Y maze and then given a footshock in 1 arm of the maze. The rats t hen received bilateral injections of lidocaine or buffer into the NTS and peripheral injections of saline or epinephrine (0.01 or 0.05 mg/kg ip). Two tests were given 24 and 48 hr after training to assess reten tion in the presence and absence of contextual cues (the stainless ste el floor) associated with the footshock training trial. Epinephrine (0 .05 mg/kg) produced a significant enhancement in retention, which was attenuated by injections of lidocaine into the NTS. These findings ind icate that the NTS is involved in mediating the memory-modulating effe cts of peripheral epinephrine and that such effects are initiated at l east in part by activation of vagal afferents projecting to the NTS.