THALAMOCORTICAL OSCILLATIONS IN A GENETIC MODEL OF ABSENCE EPILEPSY
Abstract number :
E.07
Submission category :
Year :
2002
Submission ID :
3422
Source :
www.aesnet.org
Presentation date :
12/7/2002 12:00:00 AM
Published date :
Dec 1, 2002, 06:00 AM
Authors :
Virginia Tancredi, Giovanna D[ssquote]Arcangelo, Margherita D[ssquote]Antuono, Giuseppe Biagini, Claudio Frank, Massimo Avoli. Neuroscienze, Universit[agrave] di Roma [dsquote]Tor Vergata[dsquote] Italy, Roma, Italy; IRCCS Neuromed, Pozzilli (Isernia), It
RATIONALE: The neocortex and thalamus generate brain rhythms that are observed during sleep and in some pathological conditions such as absence seizures. Several studies have analysed the mechanisms of thalamocortical synchronization [italic]in vivo[/italic] and [italic]in vitro[/italic]. However, it is as yet unclear how reciprocal thalamocortical network interactions contribute to absence seizures. Here, we addressed this issue by thalamocortical slices obtained from epileptic ([gt]160 days old) WAG/Rij and age-matched, non-epileptic control (NEC) rats.
METHODS: We used field potential recordings in an [italic]in vitro[/italic] thalamocortical slice preparation (Tancredi et al., J. Neurophysiol., 84: 1093-1097, 2000). To increase neuronal excitability, and thus to cause the appearance of spontaneous field potential activity in vitro, we applied medium containing low concentrations of the K+ channel blocker 4-aminopyridine (4AP, 0.5-5[mu]M).
RESULTS: Sequences of fast (intra-burst frequency=10-16Hz) and slow (5-8Hz) spindle-like oscillations (SLOs) were recorded in WAG/Rij slices during application of 4AP. In contrast, only fast SLOs (9-16Hz) were seen in NEC slices. Moreover, in WAG/Rij slices, slow SLOs were of larger amplitude and reflected a larger degree of synchronization than fast SLOs. Slow SLOs were not seen after surgical separation of cortex and thalamus; under these conditions fast SLOs continued to occur in thalamus only. Fast and slow SLOs disappeared in all areas of the WAG/Rij slice during thalamic application of the excitatory amino acid receptor antagonist kynurenic acid; by contrast, fast SLOs were still recorded in the ventrobasal complex when kynurenic acid was applied to the cortex.
CONCLUSIONS: Our data demonstrate for the first time that highly synchronized, slow SLOs are induced by 4AP in WAG/Rij, but not in NEC slices. This slow activity, which may represent an [italic]in vitro[/italic] hallmark of thalamocortical epileptogenicity, requires the function of reciprocally connected thalamic and cortical networks.
[Supported by: Canadian Institutes of Health Research and Savoy Foundation.]