Effects of dextroamphetamine on event-related slow potentials in rat cortex during a reaction time task

Event-related slow potentials were recorded from two different cortical areas in the rat during an operant reaction time task in which trials were initiated at variable intervals by an auditory warning stimulus. Slow potential responses during the 2-sec period between onset of the warning stimulus and extension of a retractable lever were analyzed. The effects of various doses of d-Amphetamine on the slow potential responses were examined. Surface-negative slow potential responses from the frontal cortex had two components, an early wave which reached maximum amplitude at 200–350 msec after the stimulus and a later wave which began at 650–850 msec. The slow potential response recorded from the visual cortex showed a smaller surface-negative wave which was maximum at 350–1000 msec; following the initial negative wave, the potential gradually shifted positive. d-Amphetamine (0.25, 0.5 and 1.0 mg/kg) caused a dose-related depression of the frontal slow potential responses (indicated by both amplitude and area analysis). Amplitudes and areas of the visual slow potential were not consistently altered. The results of this study indicate that the effects of d-amphetamine on eventrelated slow potentials in the rat are dependent on the cortical area from which they are recorded.