Temporal sequence of ictal discharges propagation in the corticolimbic basal ganglia system during amygdala kindled seizures in freely moving rats

Abstract

We used a multiple channel, single unit recording technique to investigate the neural activity in different corticolimbic and basal ganglia regions in freely moving rats before and during generalized amygdala kindled seizures. Neural activity was recorded simultaneously in the sensorimotor cortex (Ctx), hippocampus, amygdala, substantia nigra pars reticulata (SNr) and the subthalamic nucleus (STN). We observed massive synchronized activity among neurons of different brain regions during seizure episodes. Neurons in the kindled amygdala led other regions in synchronized firing, revealed by time lags of neurons in other regions in crosscorrelogram analysis. While there was no obvious time lag between Ctx and SNr, the STN and hippocampus did lag behind the Ctx and SNr in correlated firing. Activity in the amygdala and SNr contralateral to the kindling stimulation site lagged behind their ipsilateral counterparts. However no time lag was found between the kindling and contralateral sides of Ctx, hippocampus and STN. Our data confirm that the amygdala is an epileptic focus that emits ictal discharges to other brain regions. The observed temporal pattern indicates that ictal discharges from the amygdala arrive first at Ctx and SNr, and then spread to the hippocampus and STN. The simultaneous activation of both sides of the Ctx suggests that the neocortex participates in kindled seizures as a unisonant entity to provoke the clonic motor seizures. Early activation of the SNr (before the STN and hippocampus) points to an important role of the SNr in amygdala kindled seizures and supports the view that different SNr manipulations may be effective ways to control seizures.

Changes in Granule Cell Firing Rates Precede Locally Recorded Spontaneous Seizures by Minutes in an Animal Model of Temporal Lobe Epilepsy

“…Hippocampal unit activity has been recorded and analyzed in animal models of temporal lobe epilepsy while kindling (Shi et al 2007) and during latent (Sanchez et al 2006), interictal (Liu et al 2003), and postictal periods (Zhou et al 2007), but not during spontaneous seizures. In patients with temporal lobe epilepsy, unit recordings have been obtained from the mesial temporal lobe during spontaneous seizures (Babb and Crandall 1976;Babb et al 1987;Verzeano et al 1971).…”

Neuroprotective Effect of Piperine on Primarily Cultured Hippocampal Neurons

“…21) Massive synchronized firings were observed among neurons of sensorimotor cortex, hippocampus, amygdalae and subthalamic nucleus during seizure episodes. 22) It is well accepted that the hippocampus is critical in the formation of declarative memories. Interestingly, electrophysiological studies demonstrated that this region also has a particularly low seizure threshold, where globally synchronous synaptic activity occurred.…”

The role of the substantia nigra pars reticulata in kindling resistance in rats with genetic absence epilepsy

“…In kindling induced seizures, the SNR controls the transition from limbic to generalized motor seizures. 30-32 In the SNR of adult male rats, infusions of GABA A receptor agonists in the SNR anterior and SNR posterior subregions mediate separate inhibitory or facilitatory effects respectively on the onset, propagation and/or termination of generalized seizures. 11,33 Veliskova et al 34 found that in the flurothyl-induced generalized seizures in rats, the SNR posterior subregion was selectively active during the pre-clonic period while the SNR anterior was not involved at this stage.…”