ELECTRICAL ACTIVITY OF THE PREPYRIFORM CORTEX AFTER RESERPINE IN THE RAT

¹ Department of Physiology, University of California, Berkeley, California

The effects of 4 doses of reserpine (0.5, 0.05, 0.01 and 0.001 mg/kg i.p.) on the spontaneous and evoked electrical activity of the prepyriform cortex were investigated in unanesthetized,unrestrained rats chronically implanted with electrodes.

Prepyriform spontaneous activity is characterized by bursts of sinusoidal waves with an average wave frequency of 50 cycles/second, and by slow waves coincident with respiration. After reserpine (0.01 to 0.5 mg/kg), the folowing changes in the prepyriform spontaneous activity were observed: a decrease in amplitude and an increase in frequency of the fast sinusoidal waves, and a decrease in frequency of the respiratory waves. Frequently, the normal fast and slow waves were replaced by high amplitude slow waves which were generated by this cortex 2 to 4 hours after the higher doses of reserpine.

The prepyriform averaged evoked potential, produced by single shock stimulation of the lateral olfactory tract, resembles a damped sinusoidal oscillation. Amplitudes of the first three deflections of the potential were depressed 2 to 4 hours after the 3 highest doses of reserpine. Start and peak latencies of the evoked response remained unchanged after all doses.

The changes in the prepyriform spontaneous and evoked electrical activity indicate that reserpine depresses the olfactory cortex, either by a direct or indirect action.