Essential functions of central nervous system astrocytes include providing structural support to the neuropil and maintenance of extracellular neurotransmitter and ion concentrations. However, this glial cell type has also been shown to actively modify synaptic transmission by secreting a number of signaling molecules. The mechanism by which these signaling molecules are released, in many cases, depends on robust increases in intracellular calcium concentration ([Ca2+ ]i) that are initiated following activation of membrane bound receptors. While much is now known about calcium signaling in astrocytes in normal brain, very little is understood about the mechanisms underlying intracellular calcium signaling in reactive astrocytes in neurological disorders such as temporal lobe epilepsy (TLE). We recently discovered that in a rat model of status epilepticus (SE)-induced TLE, reactive astrocytes dramatically increase the expression of a number of kainate receptor (KAR) subunits. We hypothesize that activation of functional KARs would provide a novel signaling mechanism for initiation of [Ca2+]i changes in these reactive astrocytes.
Specific Aim 1 ofthe proposal will use immunohistochemistry and immunoblotting techniques to determine if SE results in a long- term increase in the expression of KAR in astrocytes.
Specific Aim 2 will use multi-photon microscopy and calcium imaging of astrocytes in acute hippocampal brain slices to determine if activation of KARs triggers [Ca2+]i changes. In addition, we will determine if [Ca2+]i changes in reactive astrocytes are altered in magnitude, frequency, and/or spatial distribution when compared to astrocytes from hippocampal brain slices of control rats. It is anticipated that results from the proposed experiments will shed significant light on the function of astrocytes in TLE and ultimately lead to the development of novel molecular targets for innovative therapeutic approached for the treatment, prevention, and/or cure of this seizure disorder. Increasing evidence suggests that non-neuronal glial cells may contribute to seizure generation and epilepsy. Therefore, the proposed research will evaluate changes in a specific type of excitatory amino acid receptor that occur in glial cells in an animal model of temporal lobe epilepsy. It is anticipated that this work will reveal new potential therapeutic targets for the treatment of epilepsy.
| Wilcox, Karen S; Dixon-Salazar, Tracy; Sills, Graeme J et al. (2013) Issues related to development of new antiseizure treatments. Epilepsia 54 Suppl 4:24-34 |
| Vargas, Jay R; Takahashi, D Koji; Thomson, Kyle E et al. (2013) The expression of kainate receptor subunits in hippocampal astrocytes after experimentally induced status epilepticus. J Neuropathol Exp Neurol 72:919-32 |
| Gibbons, M B; Smeal, R M; Takahashi, D K et al. (2013) Contributions of astrocytes to epileptogenesis following status epilepticus: opportunities for preventive therapy? Neurochem Int 63:660-9 |
| Takahashi, D K; Vargas, J R; Wilcox, K S (2010) Increased coupling and altered glutamate transport currents in astrocytes following kainic-acid-induced status epilepticus. Neurobiol Dis 40:573-85 |
