Inhibition of adenylyl cyclase in amygdala blocks the effect of audiogenic seizure kindling in genetically epilepsy-prone rats

Genetically epilepsy-prone rats of the severe seizure strain (GEPR-9s) exhibit audiogenic seizures (AGS) beginning with wild running and ending with tonic hind limb extension (TE). AGS kindling in GEPR-9s involves periodic repetition of ≥14 seizures over 7–21 days and results in prolonged seizures and an additional phase of generalized post-tonic clonus (PTC) that follows TE. AGS kindling behavior changes are long-lasting and involve expansion of the requisite seizure neuronal network from the brainstem to include the amygdala, mediated by neuroplasticity in lateral amygdala. Recent evidence indicates that focal activation of adenylyl cyclase (AC) in lateral amygdala leads to precipitous acquisition of AGS-kindled seizure behaviors, suggesting that activation of AC activity is important in development and maintenance of AGS kindling. The present study further examined the role of AC in AGS-kindled seizures in GEPR-9s by focally inhibiting AC in the amygdala. Bilateral microinjection of an AC inhibitor, SQ22,536 (0.25 and 0.50 nmol/side), in AGS-kindled GEPR-9s selectively blocked PTC during AGS at 1 h after microinjection, but the pre-kindled AGS behaviors remained intact. The incidence of PTC during AGS returned to pre-drug levels 12 h after the lower dose of SQ22,536 (0.25 nmol/side). However, after the higher dose of SQ22,536 (0.5 nmol/side), complete return to AGS with PTC was seen in all GEPR-9s at 120 h. These results indicate that maintenance of AGS kindling-mediated PTC in GEPR-9s may involve activation of AC. These data provide further evidence for the involvement of AC in the epileptogenic mechanisms subserving AGS kindling.