Abstract
Status epilepticus (SE), a pro-epileptogenic brain insult in rodent models of temporal lobe epilepsy, is successfully induced by pilocarpine in some, but not all, rats. This study aimed to identify characteristic alterations within the hippocampal neural network prior to the onset of SE. Sixteen microwire electrodes were implanted into the left hippocampus of male Sprague-Dawley rats. After a 7-day recovery period, animal behavior, hippocampal neuronal ensemble activities, and local field potentials (LFP) were recorded before and after an intra-peritoneal injection of pilocarpine (350 mg/kg). The single-neuron firing, population neuronal correlation, and coincident firing between neurons were compared between SE (n = 9) and nonSE rats (n = 12). A significant decrease in the strength of functional connectivity prior to the onset of SE, as measured by changes in coincident spike timing between pairs of hippocampal neurons, was exclusively found in SE rats. However, single-neuron firing and LFP profiles did not show a significant difference between SE and nonSE rats. These results suggest that desynchronization in the functional circuitry of the hippocampus, likely associated with a change in synaptic strength, may serve as an electrophysiological marker prior to SE in pilocarpine-treated rats.
Highlights
Temporal lobe epilepsy (TLE) is a common type of partial epilepsy, and its development can be triggered by an initial brain damaging insult such as traumatic brain injury, stroke, cerebral tumor, and status epilepticus (SE) [1]
The local field potentials (LFP) was recorded for 90 minutes following pilocarpine injection to show the electrographic patterns in SE and nonSE rats (Fig. 3)
This study focused on hippocampal activity in the early pre-SE period of pilocarpine-treated rats
Summary
Temporal lobe epilepsy (TLE) is a common type of partial epilepsy, and its development can be triggered by an initial brain damaging insult such as traumatic brain injury, stroke, cerebral tumor, and status epilepticus (SE) [1]. The duration and magnitude of the initial SE have been thought to be important factors contributing to subsequent development of SRS after a latent period [6,7,8]. After the application of the same dose of pilocarpine, SE is successfully induced in only a subset of experimental rats [9,10,11,12], which suggests the existence of inter-individual differences in vulnerability to the same excitotoxic insult.
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