Palizvan MR, Fathollahi Y, Semnanian S. Epileptogenic insult causes a shift in the form of long-term potentiation expression.
Neuroscience 2005;
134:415-23. [PMID:
15961249 DOI:
10.1016/j.neuroscience.2005.04.016]
[Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2005] [Revised: 03/13/2005] [Accepted: 04/16/2005] [Indexed: 11/24/2022]
Abstract
The relationship between epilepsy, modeled here by pentylenetetrazol kindling, and learning deficits, modeled here by long-term potentiation (LTP), was studied. The field excitatory postsynaptic potentials and population spikes (PS) were recorded from strata radiatum and pyramidale, respectively, in urethane-anesthetized rat dorsal hippocampus CA1 area upon stimulation of Schaffer collaterals. To induce LTP, a 100 Hz primed-burst stimulation protocol was used. Experiments were carried out at approximately 30 days after the last pentylenetetrazol dose. The effects of voltage dependent calcium channel blocker verapamil and N-methyl-D-aspartate receptor antagonist MK-801 on LTP expression were examined. Tetanic stimulation elicited both field excitatory postsynaptic potential LTP and PS LTP in control animals, and LTP-induction of the PS in control animals was attenuated by MK-801, but not by verapamil. By contrast, kindled rats showed LTP of the PS only. MK-801 reduced the extent of potentiation of PS amplitude and verapamil inhibited the PS amplitude potentiation, completely. The results suggest that seizure induction modifies mechanisms underlying LTP induction and causes a shift in the form of LTP expression. The pentylenetetrazol-kindling-induced increase in PS LTP is sensitive to verapamil and not to MK-801 and therefore primarily dependent on activation of voltage dependent calcium channels rather N-methyl-D-aspartate receptors. Kindling may lead to a shift in synaptic plasticity thresholds much like the shift that occurs during aging, and such alterations may contribute to deficits in learning and memory.
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