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The antiepileptogenic effect of low-frequency stimulation on perforant path kindling involves changes in regulators
Simin Namvar1, Yaghoub Fathollahi1, Mohammad Javan1
1Department of Physiology, Faculty of Medical Sciences, Tarbiat Modares University, Tehran, Iran.
Abstract:
G-protein coupled receptors may have a role in mediating the antiepileptogenic effect of low-frequency stimulation (LFS) on kindling acquisition. This effect is accompanied by changes at the intracellular level of cAMP. In the present study, the effect of rolipram as a phosphodiesterase inhibitor on the antiepileptogenic effect of LFS was investigated. Meanwhile, the expression of αs- and αi-subunit of G proteins and regulators of G-protein signaling (RGS) proteins following LFS application was measured. Male Wistar rats were kindled by perforant path stimulation in a semi-rapid kindling manner (12 stimulations per day) during a period of 6days. Application of LFS (0.1ms pulse duration at 1Hz, 200 pulses, 50-150μA, 5min after termination of daily kindling stimulations) to the perforant path retarded the kindling development and prevented the kindling-induced potentiation and kindling-induced changes in paired pulse indices in the dentate gyrus. Intra-cerebroventricular microinjection of rolipram (0.25μM) partially prevented these LFS effects. Twenty-four hours after the last kindling stimulation, the dentate gyrus was removed and changes in protein expression were measured by Western blotting. There was no significant difference in the expression of α-subunit of Gs and Gi/o proteins in different experimental groups. However, application of LFS during the kindling procedure decreased the expression RGS4 and RGS10 proteins (that reduce the activity of Gi/o) and prevented the kindling-induced decrease of RGS2 protein (which reduces the Gs activity). Therefore, it can be postulated that the Gi/o protein signaling pathways may be involved in antiepileptogenetic effect of LFS, and this is why decreasing the cAMP metabolism by rolipram attenuates this effect of LFS.
Insights
Low-frequency stimulation (LFS) has an antiepileptogenic effect, potentially mediated by G-protein coupled receptors. Inhibiting phosphodiesterase with rolipram partially blocked this LFS effect, suggesting G-protein signaling involvement.
Area of Science:
- Neuroscience
- Epilepsy Research
- Molecular Biology
Background:
- G-protein coupled receptors (GPCRs) are implicated in the antiepileptogenic effects of low-frequency stimulation (LFS).
- LFS-induced antiepileptogenesis is associated with intracellular cyclic adenosine monophosphate (cAMP) level alterations.
- The role of specific G-protein subunits and regulators of G-protein signaling (RGS) proteins in this process requires further elucidation.
Purpose of the Study:
- To investigate the effect of rolipram, a phosphodiesterase inhibitor, on the antiepileptogenic effects of LFS in a rat kindling model.
- To examine the impact of LFS on the expression of G-protein αs- and αi-subunits and RGS proteins in the dentate gyrus.
- To elucidate the involvement of specific G-protein signaling pathways in LFS-mediated antiepileptogenesis.
Main Methods:
- Male Wistar rats underwent a semi-rapid kindling protocol via perforant path stimulation over 6 days.
- Low-frequency stimulation (LFS) was applied to the perforant path post-kindling stimulation.
- Intra-cerebroventricular microinjection of rolipram was administered, and protein expression (G-protein subunits, RGS proteins) in the dentate gyrus was analyzed via Western blotting.
Main Results:
- LFS significantly retarded kindling acquisition and prevented kindling-induced potentiation and paired pulse index changes in the dentate gyrus.
- Intra-cerebroventricular rolipram partially attenuated the antiepileptogenic effects of LFS.
- LFS decreased the expression of RGS4 and RGS10 proteins, while preventing the kindling-induced decrease in RGS2 protein expression. No significant changes were observed in Gs and Gi/o protein subunit expression.
Conclusions:
- G-protein signaling, particularly involving the G-protein alpha i/o (Gi/o) subunit pathways, plays a role in the antiepileptogenic effect of LFS.
- Modulation of cAMP metabolism by phosphodiesterase inhibition with rolipram attenuates the antiepileptogenic effects of LFS, supporting the involvement of cAMP-related signaling cascades.
- RGS proteins, specifically RGS4, RGS10, and RGS2, are differentially regulated by LFS and kindling, further implicating their role in modulating G-protein activity during epileptogenesis.
