DIFFERENTIAL SENSITIVITY OF VARIOUS TEMPORAL-LOBE STRUCTURES IN THE RAT TO KINDLING AND STATUS EPILEPTICUS INDUCTION

Using focal brain stimulation (kindling), discrete seizures can be tri ggered from many neuroanatomic sites with varying degrees of facility. From several of these sites, protracted seizures or status epilepticu s (SE) also can be triggered. To date, no comparison has been made bet ween different brain sites in their sensitivity both to kindling and t o SE development. In this report, we have compared the kindling profil es of three amygdala nuclei, namely the basal (BL), central (CE), and medial (ME) nuclei, to the adjacent piriform (PIR) and perirhinal (PRH ) cortices. In addition, three weeks following kindling, the susceptib ility of each kindled site to status epilepticus (SE) was assessed by exposing the site to 60 min of electrical stimulation. We observed tha t (a) during the course of daily kindling, the afterdischarge threshol d dropped progressively and significantly in all structures, (b) the r ate of kindling in the PRH and PIR cortices and the CE amygdala was si gnificantly faster than either the BL or ME amygdala, (c) when discret e convulsions were triggered, the latency to forelimb clonus in the PR H cortex and CE amygdala was significantly shorter than the other thre e structures, and (d) despite being slower to kindle than most other s ites, stimulation of the BL nucleus most readily triggered SE. The kin dling data suggest that discharges triggered from the PRH and CE more readily access motor systems supporting limbic convulsions than discha rges triggered from the BL, ME nuclei or the PIR cortex, On the other hand, the SE data indicate that the mechanisms and circuits associated with the development of discrete kindled seizures are not identical t o those associated with the induction of limbic SE.