Of the Mechanisms of Paroxysmal Depolarization Shifts: Generation and Maintenance of Bicuculline-Induced Paroxysmal Activity in Rat Hippocampal Cell Cultures

Denis P Laryushkin; Sergei A Maiorov; Valery P Zinchenko; Valentina N Mal'tseva; Sergei G Gaidin; Artem M Kosenkov

doi:10.3390/ijms241310991

Of the Mechanisms of Paroxysmal Depolarization Shifts: Generation and Maintenance of Bicuculline-Induced Paroxysmal Activity in Rat Hippocampal Cell Cultures

Int J Mol Sci. 2023 Jul 1;24(13):10991. doi: 10.3390/ijms241310991.

Authors

Denis P Laryushkin¹, Sergei A Maiorov¹, Valery P Zinchenko¹, Valentina N Mal'tseva¹, Sergei G Gaidin¹, Artem M Kosenkov¹

Affiliation

¹ Federal Research Center "Pushchino Scientific Center for Biological Research of the Russian Academy of Sciences", Institute of Cell Biophysics of the Russian Academy of Sciences, 142290 Pushchino, Russia.

Abstract

Abnormal depolarization of neuronal membranes called paroxysmal depolarization shift (PDS) represents a cellular correlate of interictal spikes. The mechanisms underlying the generation of PDSs or PDS clusters remain obscure. This study aimed to investigate the role of ionotropic glutamate receptors (iGluRs) in the generation of PDS and dependence of the PDS pattern on neuronal membrane potential. We have shown that significant depolarization or hyperpolarization (by more than ±50 mV) of a single neuron does not change the number of individual PDSs in the cluster, indicating the involvement of an external stimulus in PDS induction. Based on this data, we have suggested reliable protocols for stimulating single PDS or PDS clusters. Furthermore, we have found that AMPA (α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid) receptors are necessary for PDS generation since AMPAR antagonist NBQX completely suppresses bicuculline-induced paroxysmal activity. In turn, antagonists of NMDA (N-methyl-D-aspartate) and kainate receptors (D-AP5 and UBP310, respectively) caused a decrease in the amplitude of the first action potential in PDSs and in the amplitude of the oscillations of intracellular Ca²⁺ concentration occurring alongside the PDS cluster generation. The effects of the NMDAR (NMDA receptor) and KAR (kainate receptor) antagonists indicate that these receptors are involved only in the modulation of paroxysmal activity. We have also shown that agonists of some G_i-coupled receptors, such as A₁ adenosine (A₁Rs) or cannabinoid receptors (CBRs) (N₆-cyclohexyladenosine and WIN 55,212-2, respectively), completely suppressed PDS generation, while the A₁R agonist even prevented it. We hypothesized that the dynamics of extracellular glutamate concentration govern paroxysmal activity. Fine-tuning of neuronal activity via action on G_i-coupled receptors or iGluRs paves the way for the development of new approaches for epilepsy pharmacotherapy.

Keywords: AMPA receptors; Gi-coupled receptors; NMDA receptors; kainate receptors; paroxysmal depolarization shift (PDS).

MeSH terms

Action Potentials
Animals
Bicuculline / pharmacology
Hippocampus*
Neurons
Rats
Receptors, N-Methyl-D-Aspartate*
alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid / pharmacology

Substances

Bicuculline
Receptors, N-Methyl-D-Aspartate
alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid

Grants and funding

22-25-00659/Russian Science Foundation