Sah, Nirnath and Sikdar, Sujit K (2013) Transition in subicular burst firing neurons from epileptiform activity to suppressed state by feedforward inhibition. In: EUROPEAN JOURNAL OF NEUROSCIENCE, 38 (4). pp. 2542-2556.
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The subiculum, a para-hippocampal structure positioned between the cornu ammonis 1 subfield and the entorhinal cortex, has been implicated in temporal lobe epilepsy in human patients and in animal models of epilepsy. The structure is characterized by the presence of a significant population of burst firing neurons that has been shown previously to lead epileptiform activity locally. Phase transitions in epileptiform activity in neurons following a prolonged challenge with an epileptogenic stimulus has been shown in other brain structures, but not in the subiculum. Considering the importance of the subicular burst firing neurons in the propagation of epileptiform activity to the entorhinal cortex, we have explored the phenomenon of phase transitions in the burst firing neurons of the subiculum in an in vitro rat brain slice model of epileptogenesis. Whole-cell patch-clamp and extracellular field recordings revealed a distinct phenomenon in the subiculum wherein an early hyperexcitable state was followed by a late suppressed state upon continuous perfusion with epileptogenic 4-aminopyridine and magnesium-free medium. The suppressed state was characterized by inhibitory post-synaptic potentials in pyramidal excitatory neurons and bursting activity in local fast-spiking interneurons at a frequency of 0.1-0.8Hz. The inhibitory post-synaptic potentials were mediated by GABA(A) receptors that coincided with excitatory synaptic inputs to attenuate action potential discharge. These inhibitory post-synaptic potentials ceased following a cut between the cornu ammonis 1 and subiculum. The suppression of epileptiform activity in the subiculum thus represents a homeostatic response towards the induced hyperexcitability. Our results suggest the importance of feedforward inhibition in exerting this homeostatic control.
| Item Type: | Journal Article |
|---|---|
| Publication: | EUROPEAN JOURNAL OF NEUROSCIENCE |
| Publisher: | WILEY-BLACKWELL |
| Additional Information: | Copyright of this article is belongs to |
| Keywords: | epileptiform activity; feedforward inhibition; GABA(A) receptors; rat subiculum |
| Department/Centre: | Division of Biological Sciences > Molecular Biophysics Unit |
| Date Deposited: | 02 Oct 2013 05:47 |
| Last Modified: | 02 Oct 2013 05:47 |
| URI: | http://eprints.iisc.ac.in/id/eprint/47354 |
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