Epileptic discharges manifest in individual neurons as abnormal membrane potential fluctuations called paroxysmal depolarization shift (PDS). PDSs can combine into clusters that are accompanied by synchronous oscillations of the intracellular Ca²⁺ concentration ([Ca²⁺]_i) in neurons. Here, we investigate the contribution of L-type voltage-gated calcium channels (VGCC) to epileptiform activity induced in cultured hippocampal neurons by GABA(A)R antagonist, bicuculline. Using KCl-induced depolarization, we determined the optimal effective doses of the blockers. Dihydropyridines (nifedipine and isradipine) at concentrations ≤ 10 μM demonstrate greater selectivity than the blockers from other groups (phenylalkylamines and benzothiazepines). However, high doses of dihydropyridines evoke an irreversible increase in [Ca²⁺]_i in neurons and astrocytes. In turn, verapamil and diltiazem selectively block L-type VGCC in the range of 1–10 μM, whereas high doses of these drugs block other types of VGCC. We show that L-type VGCC blockade decreases the half-width and amplitude of bicuculline-induced [Ca²⁺]_i oscillations. We also observe a decrease in the number of PDSs in a cluster and cluster duration. However, the pattern of individual PDSs and the frequency of the cluster occurrence change insignificantly. Thus, our results demonstrate that L-type VGCC contributes to maintaining the required [Ca²⁺]_i level during oscillations, which appears to determine the number of PDSs in the cluster.

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.

Gi-coupled receptors, particularly cannabinoid receptors (CBRs), are considered perspective targets for treating brain pathologies, including epilepsy. However, the precise mechanism of the anticonvulsant effect of the CBR agonists remains unknown. We have found that WIN 55,212-2 (a CBR agonist) suppresses the synchronous oscillations of the intracellular concentration of Ca²⁺ ions (epileptiform activity) induced in the neurons of rat hippocampal neuron-glial cultures by bicuculline or NH₄Cl. As we have demonstrated, the WIN 55,212-2 effect is mediated by CB₁R receptors. The agonist suppresses Ca²⁺ inflow mediated by the voltage-gated calcium channels but does not alter the inflow mediated by NMDA, AMPA, and kainate receptors. We have also found that phospholipase C (PLC), protein kinase C (PKC), and G-protein-coupled inwardly rectifying K⁺ channels (GIRK channels) are involved in the molecular mechanism underlying the inhibitory action of CB₁R activation against epileptiform activity. Thus, our results demonstrate that the antiepileptic action of CB₁R agonists is mediated by different intracellular signaling cascades, including non-canonical PLC/PKC-associated pathways.

Background/Objectives: Polysaccharides are complex molecules with a wide range of biological activities that can be used in various biomedical applications. In this work, the antiulcer effect and influence on the level of pro- and anti-inflammatory cytokines of Solanum tuberosum L. polysaccharide (STP) were studied. Methods: The antiulcer effect of STP was studied in the Okabe chronic peptic ulcer model by evaluating the influence of STP on the ulcer index in Wistar rats, comparing it to omeprazole and ranitidine. Dose-effect analysis was also carried out. The level of pro- and anti-inflammatory cytokines was studied using ELISA kits. Results: After treatment in the polysaccharide groups, ulcer healing is observed in 60–80% of cases, in the omeprazole group in 50%, and in the ranitidine group in 25%. STP intravenous injections lead to the formation of a more differentiated mucous membrane; no coarse scar tissue is formed, which is typical for control and comparison drugs. Glycan causes a significant acceleration of the healing of experimental peptic ulcers in rats. STP appears to modulate pro- and anti-inflammatory cytokines. On the fourth and tenth days, a significant decrease in the levels of pro-inflammatory cytokines IL-1b and IFN-γ was noted in the polysaccharide group compared to the control group, while the level of anti-inflammatory cytokine IL-4 significantly increased. Conclusions: Intravenous administration of STP leads to the restoration of functionality and effective tissue regeneration. The antiulcer activity of STP is based on the regulation of the pro- and anti-inflammatory balance.

COVID-19 is a highly contagious respiratory disease with a high number of lethal cases in humans, which causes the need to search for new therapeutic agents. Polysaccharides could be one of the prospective types of molecules with a large variety of biological activities, especially antiviral. The aim of this work was to study the specific antiviral activity of the drug “Immeran” on a model of a new coronavirus infection SARS-CoV-2 in hamsters. Based on the second experiment, intraperitoneal treatment with the drug according to a treatment regimen in doses of 500 and 1000 μg/kg (administration after an hour, then once a day every other day, a total of 3 administrations) was effective, reliably suppressing the replication of the virus in the lungs and, at a dose of 1000 μg/kg, prevented weight loss in animals. In all cases, the treatment stimulated the formation of virus-neutralizing antibodies to the SARS-CoV-2 virus, which suggests that the drug possesses adjuvant properties.