Showing papers by "Pavel M. Balaban published in 2022"

Contribution of histone acetylation to the serotonin-mediated long-term synaptic plasticity in terrestrial snails.

Abstract: Serotonin plays a decisive role in long-term synaptic plasticity and long-term memory in mollusks. Previously, we demonstrated that histone acetylation is a regulatory mechanism of long-term memory in terrestrial snail. At the behavioral level, many studies were done in Helix to elucidate the role of histone acetylation and serotonin. However, the impact of histone acetylation on long-term potentiation of synaptic efficiency in electrophysiological studies in Helix has been studied only in one paper. Here we investigated effects of serotonin, histone deacetylases inhibitors sodium butyrate and trichostatin A, and a serotonergic receptor inhibitor methiothepin on long-term potentiation of synaptic responses in vitro. We demonstrated that methiothepin drastically declined the EPSPs amplitudes when long-term potentiation was induced, while co-application either of histone deacetylase inhibitors sodium butyrate or trichostatin A with methiothepin prevented the weakening of potentiation. We showed that single serotonin application in combination with histone deacetylase blockade could mimic the effect of repeated serotonin applications and be enough for sustained long-lasting synaptic changes. The data obtained demonstrated that histone deacetylases blockade ameliorated deficits in synaptic plasticity induced by different paradigms (methiothepin treatment, the weak training protocol with single application of serotonin), suggesting that histone acetylation contributes to the serotonin-mediated synaptic plasticity.

Amyloid Aβ25-35 Aggregates Say ‘NO’ to Long-Term Potentiation in the Hippocampus through Activation of Stress-Induced Phosphatase 1 and Mitochondrial Na+/Ca2+ Exchanger

Abstract: The search for strategies for strengthening the synaptic efficiency in Aβ25-35-treated slices is a challenge for the compensation of amyloidosis-related pathologies. Here, we used the recording of field excitatory postsynaptic potentials (fEPSPs), nitric oxide (NO) imaging, measurements of serine/threonine protein phosphatase (STPP) activity, and the detection of the functional mitochondrial parameters in suspension of brain mitochondria to study the Aβ25-35-associated signaling in the hippocampus. Aβ25-35 aggregates shifted the kinase–phosphatase balance during the long-term potentiation (LTP) induction in the enhancement of STPP activity. The PP1/PP2A inhibitor, okadaic acid, but not the PP2B blocker, cyclosporin A, prevented Aβ25-35-dependent LTP suppression for both simultaneous and delayed enzyme blockade protocols. STPP activity in the Aβ25-35-treated slices was upregulated, which is reverted relative to the control values in the presence of PP1/PP2A but not in the presence of the PP2B blocker. A selective inhibitor of stress-induced PP1α, sephin1, but not of the PP2A blocker, cantharidin, is crucial for Aβ25-35-mediated LTP suppression prevention. A mitochondrial Na+/Ca2+ exchanger (mNCX) blocker, CGP37157, also attenuated the Aβ25-35-induced LTP decline. Aβ25-35 aggregates did not change the mitochondrial transmembrane potential or reactive oxygen species (ROS) production but affected the ion transport and Ca2+-dependent swelling of organelles. The staining of hippocampal slices with NO-sensitive fluorescence dye, DAF-FM, showed stimulation of the NO production in the Aβ25-35-pretreated slices at the dendrite-containing regions of CA1 and CA3, in the dentate gyrus (DG), and in the CA1/DG somata. NO scavenger, PTIO, or nNOS blockade by selective inhibitor 3Br-7NI partly restored the Aβ25-35-induced LTP decline. Thus, hippocampal NO production could be another marker for the impairment of synaptic plasticity in amyloidosis-related states, and kinase–phosphatase balance management could be a promising strategy for the compensation of Aβ25-35-driven deteriorations.

Sodium Channels Involved in the Initiation of Action Potentials in Invertebrate and Mammalian Neurons

Abstract: Living organisms react to external stimuli to adapt their activity to the environment for survival. Acquired information is encoded by neurons by action potentials (APs) in a series of discrete electrical events. Rapid initiation of the AP is critical for fast reactions and strongly relies on voltage-activated Na+-selective channels (NaVs), which are widely expressed by both invertebrate and vertebrate neurons. Intuitively, NaVs of higher mammals should be activated faster than those of any other species. In addition to improved NaV channel structure, central mammalian neurons also demonstrate a patterned distribution of specific types of NaV1 channels at and near the site of AP initiation within the axonal initial segment (AIS). The AIS has different types of fast Nav1 channels and is thought to provide the biological basis for efficient frequency coding of information. In the present work, we review data related to the channels underlying fast initiation of action potentials in vertebrates and invertebrates, along with their evolution, distribution, and known specific roles. Current research has established that all mammalian NaV1 (1.1–1.9) channels share a similar structure, with 4 conservative transmembrane D-domains with a highly homologous sequence, but significant differences in the length of the functional cytoplasmic linkers. Similarly, the structure of NaV1 channels in invertebrates is generally similar to that of mammals, but it shows high variability across the evolutionary tree in the length of the linkers. AP initiation in mammalian cortical neurons is mediated by NaV1.2 and NaV1.6 channels, whereas interneurons mostly rely on NaV1.1 channels in their firing. Although invertebrate NaV1 channels normally display relatively slow kinetics, their activation is fast enough to produce APs, even in simple animals such as Placozoa. Remarkably, fast sodium-based excitability is not limited to animals. Recently, a photosynthetic prokaryote has been found to show rapidly activated sodium currents provided by their independently evolved single D-domain EuKatB sodium channels.