Task-dependent effects of the antidepressant/antipanic drug phenelzine on memory

Phenelzine (PLZ) is a non-selective monoamine oxidase (MAO) inhibitor commo nly used to treat depression and panic disorder. In addition to increasing levels of biogenic amines in the brain, PLZ elevates brain levels of the am ino acid gamma-aminobutyric acid (GABA; Baker et al. 1991; present study). Given the extensive evidence implicating biogenic amines and GABA in mnemon ic processes, PLZ may affect learning and memory. To investigate this possi bility, male Sprague-Dawley rats were given PLZ sulfate (15 or 30 mg/kg, ba sed on free base weight) 2 h prior to training in a continuous multiple tri al inhibitory avoidance (CMIA) and spatial water maze task. Retention was a ssessed 48 h later. The results indicated that PLZ enhanced CMIA and impair ed water maze retention performance. Compared to control rats, rats given P LZ took significantly longer to re-enter the shock compartment and swam lon ger distances before reaching the escape platform on the retention tests. T hese effects of PLZ did not appear to be the result of PLZ-induced changes in acquisition or retrieval processes, activity levels, or footshock sensit ivity. Combined, these findings indicate that PLZ influences memory in a ta sk-dependent manner. These differential effects of PLZ may be the result of contrasting influences of GABA and biogenic amines on memory.