LOW-FREQUENCY STIMULATION OF AMYGDALA INHIBITS ICTOGENESIS IN THE PERIRHINAL CORTEX
Abstract number :
2.006
Submission category :
Year :
2002
Submission ID :
3396
Source :
www.aesnet.org
Presentation date :
12/7/2002 12:00:00 AM
Published date :
Dec 1, 2002, 06:00 AM
Authors :
Toshiyuki Kano, Margherita D[ssquote]Antuono, Philip de Guzman, Ruba Benini, Massimo Avoli. Neurology & Neurosurgery & Physiology, Montreal Neurological Institute/McGill University, Montreal, Quebec, Canada
RATIONALE: Low-frequency (0.5-1Hz) electrical stimulation of hippocampal outputs controls ictogenesis in the limbic system maintained in vitro in a slice preparation (Barbarosie and Avoli, 1997). This procedure may have potential therapeutical implications. Hence, we studied as to whether similar low-frequency stimuli delivered in the basolateral amygadala (BLA) could inhibit ictal discharges generated by perirhinal cortex (PC) netwoks.
METHODS: Field potential and sharp-electrode intracellular recordings were conducted within horizontal rat brain slices containing the PC and a portion of the BLA. Connections with the hippocampus proper were surgically separated. Epileptiform activity was induced by bath applying the convulsant drug 4-aminopyridine (4AP, 50[mu]M). Electrical stimuli were delivered in BLA through bipolar tungsten electrodes.
RESULTS: Electrical stimuli applied to the BLA under control conditions elicited monosynaptic excitatory responses in neurons recorded in the middle layers of the PC. Following addition of 4AP to the bathing medium, ictal discharges (duration=up to 40s) appeared in both BLA and PC. This epileptiform activity was characterized by prolonged, NMDA receptor-dependent depolarizations in regularly firing PC neurons. Moreover, cutting the connections between PC and BLA made independent interictal and ictal discharges occur in both structures. In PC/BLA connected slices, after addition of 4AP, repetitive stimulation at frequencies [gte] 0.5 Hz decreased and eventually blocked the ictal activity recorded in PC.
CONCLUSIONS: These results show that reciprocally connected BLA/PC networks generate ictal discharges in response to bath application of 4AP. These events, which resemble the electrographic limbic seizures seen in mesial temporal lobe epilepsy patients, can originate independently in either BLA or PC. Moreover, we have demonstrated here that repetitive, low frequency activation of BLA outputs directed to the PC, can control ictogenesis in this limbic area.
[Supported by: Canadian Institutes of Health Research and Savoy Foundation.]