LONG-LASTING CHANGES IN THE ORIGIN OF SPONTANEOUS DISCHARGES FROM AMYGDALA-KINDLED RATS - PIRIFORM VS PERIRHINAL CORTEX IN-VITRO

The origin of spontaneous field potentials in coronal slices of the am ygdala-piriform-perirhinal area (A-P area) from amygdala-kindled and c ontrol rats was assessed. In Expt. 1, the field potentials initially o riginated in the perirhinal (PRh) cortex of control tissue while they originated in the piriform (Pir) cortex of amygdala-kindled tissue. In Expt. 2, this kindling-based change was observed in the A-P area ipsi lateral but not contralateral to the kindled amygdala. In both experim ents, subsequent exposure to perfusion medium containing 0 Mg2+ result ed in the genesis of strong discharges in both control and kindled tis sues. After 2-3 h of such treatment, the origin of spontaneous dischar ges in control tissue changed from the PRh to the Pir area and persist ed in a reduced form during reperfusion with medium containing Mg2+. T his change in origin of the discharges in control tissue appeared simi lar to that seen in previously kindled tissue. In Expt. 3, during expo sure to 0 Mg2+, the response of the basolateral amygdala (BLA) was com pared with the Pir and PRh areas. Independent of the PRh discharge, th e BLA discharge closely followed the Pir discharge both in time and mo rphology. These lasting changes in the ipsilateral A-P area in vitro m ust be related in vivo to the change which allows the kindled A-P area to participate in the triggering of generalized limbic-kindled convul sions.