FURTHER CHARACTERIZATION OF KINDLING ANTAGONISM

Alternating stimulation of two sites in the forebrain culminates in ty pical kindling of generalized seizures from one site (dominant), where as the other site (suppressed) supports only nongeneralized seizures f or as long as stimulation of the dominant site continues, a phenomenon referred to as kindling antagonism. With the termination of stimulati on of the dominant site, however, seizures provoked from the suppresse d site eventually generalize, a progression thought to reflect the res umption of kindling from a previous point of arrest. To further assess the nature of kindling antagonism, we established antagonism between the amygdala and the septal area and subsequently evaluated the develo pment of seizures provoked by stimulation of sites distal to the domin ant site (always the amygdala). In Experiment 1, a 30-d stimulation-fr ee period imposed after the establishment of antagonism failed to resu lt in immediate generalization of seizures provoked from the suppresse d site (septal area) in seven of eight rats. Although these results su ggest that antagonism reflects an actual arrest of kindling rather tha n a transient inhibition of seizures, they are not entirely unambiguou s: Rats exposed to the prolonged stimulation-free period required only half the number of septal stimulations for the expression of a genera lized seizure as compared to rats receiving septal stimulation immedia tely after the establishment of antagonism. The latter finding is sugg estive of a transient component of antagonism. In Experiment 2, develo pment of generalized seizures from the previously naive right amygdala was virtually identical in rats previously kindled from the left amyg dala and in rats expressing antagonism between the septal area and lef t amygdala. Development of generalized seizures from the right amygdal a was faster than from the left amygdala in both groups of rats, howev er, suggesting that the expression of seizures provoked from the suppr essed site after the establishment of antagonism does not involve a ge neral impairment or enhancement of transfer. Experiment 3 revealed tha t radio-frequency lesions of the dominant site (amygdala) after the es tablishment of antagonism did not alter the subsequent development of generalized seizures from the suppressed site (septal area). This sugg ests that the expression of generalized seizures from the suppressed s ite after the establishment of kindling antagonism is not dictated by the functional state of the dominant site.