L-type voltage-sensitive Ca2+ channels (VSCCs) preferentially modulate several neuronal processes that are thought to be important in epileptogenesis, including the slow afterhyperpolarization (AHP), LTP, and trophic factor gene expression. However, little is yet known about the roles of L-type VSCCs in the epileptogenic process. Here, we used cell-attached patch recording techniques and single cell mRNA analyses to study L-type VSCCs in CA1 neurons from partially dissociated (zipper) hippocampal slices from entorhinally-kindled rats. L-type Ca2+-channel activity was reduced by > 50% at 1.5-3 months after kindling. Following recording, the same single neurons were extracted and collected for mRNA analysis using a recently developed method that does not amputate major dendritic processes. Therefore, neurons contained essentially full complements of mRNA. For each collected neuron, mRNA contents for the L-type pore-forming α1D/Cav1.3-subunit and for calmodulin were then analyzed by semiquantitative kinetic RT-PCR. L-type α1D-subunit mRNA was correlated with L-type Ca2+-channel activity across single cells, whereas calmodulin mRNA was not. Thus, these results appear to provide the first direct evidence at the single channel and gene expression levels that chronic expression of an identified Ca2+-channel type is modulated by epileptiform activity. Moreover, the present data suggest the hypothesis that down regulation of α1D-gene expression by kindling may contribute to the long-term maintenance of epileptiform activity, possibly through reduced Ca2+-dependent AHP and/or altered expression of other relevant genes.
|Number of pages||16|
|State||Published - Mar 1 2001|
Bibliographical noteFunding Information:
We thank Drs Tom Foster and Chris Norris for helpful comments on the manuscript. This work was supported in part by grants from the NIH (AG18228, AG04542, and AG10836) and funding from the Research Service, Department of Veterans Affairs.
- Gene expression
- Reverse transcriptase-polymerase chain reaction
- α subunit
ASJC Scopus subject areas
- Clinical Neurology