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Comenic acid (CA), a specific agonist of opioid-like receptors, effectively and safely relieves neuropathic pain by decreasing the NaV1.8 channel voltage sensitivity in the primary sensory neuron membrane. CA triggers downstream signaling cascades, in which the Na,K-ATPase/Src complex plays a key role. After leaving the complex, the signal diverges ‘tangentially’ and ‘radially’. It is directed ‘tangentially’ along the neuron membrane to NaV1.8 channels, decreasing the effective charge of their activation gating system. In the radial direction moving towards the cell genome, the signal activates the downstream signaling pathway involving PKC and ERK1/2. A remarkable feature of CA is its ability to modulate NaV1.8 channels, which relieves neuropathic pain while simultaneously stimulating neurite growth via the receptor-coupled activation of the ERK1/2-dependent signaling pathway.

The aim of the study was to elucidate the molecular mechanisms of modulation of the NaV1.8 channels with a synthetic tetrapeptide (Ac-RERR-NH2). Our data suggest that this substance specifically modulates the activation gating device of these channels, which are responsible for coding of pain signals. This agent (0.1 nM) has a neurite-stimulating effect, which indicates its possible physiological regeneration effect on the nervous tissue. The results obtained allow us to conclude that the agent under study can claim to be the drug substance of a safe and effective analgesic.

Endogenous digitalis-like factors were found in the mammalian and human blood. It was the starting point for the elucidation of the new non-pumping function of the Na+,K+-ATPase. It was previously well known that Na+,K+-ATPase is a pharmacological target receptor for cardiac glycosides (J.C. Skou. 1957. Biochim. Biophys. Acta, 23: 394–401). We have investigated the trophotropic effects of such agents as ouabain, epinephrine, norepinephrine, atenolol, and comenic acid using the organotypic tissue culture combined with the reconstruction of optical cross sections and confocal microscopy. It was shown that the growth zone of organotypic culture forms a multidimensional structure. Our results indicate that the cardiac glycoside ouabain applied in endogenous concentrations (10−8, 10−10 mol/L) can modulate transducer function of Na+,K+-ATPase and control the cell growth and proliferation. It was also shown that Src-kinase is involved in “endogenous” ouabain activated intracellular pathways as a series unit. Epinephrine (10−9–10−14 mol/L) and comenic acid (10−6–10−10 mol/L) were demonstrated to modulate the growth of 10- to 12-day-old chicken embryo cardiac tissue explants in a dose-dependent manner. Epinephrine and comenic acid regulate growth and proliferation of the cardiac tissue via receptor-mediated modulation Na+,K+-ATPase as a signal transducer. The trophotropic effects of the investigated agents specifically control the heart remodeling phenomenon.

The aim of the study was to elucidate the molecular mechanisms of the interconnection of the GABA-ergic and nociceptive systems at the level of the peripheral division of the CNS. The data obtained indicate that GABA does not affect the activation gating device of the NaV1.8 channel of the primary sensory neuron responsible for coding pain signals.This agent in a wide range of concentrations also does not affect the growth of neurites of sensory neurons of embryonic nervous tissue. These results confirm our assumption, expressed earlier that the asynaptic membrane of the primary nociceptive neuron is not under the control of the GABA-ergic system.

Norepinephrine, blockers of beta-adrenoreceptors, angiotensin-converting enzyme inhibitors and angiotensin I receptor blocker were investigated in organotypic tissue culture of cardiomyocytes of 10-12-day-old chicken embryos and newborn rat heart in a wide range of concentrations. The data obtained show that low concentration of norepinephrine led to the cardiomyocyte growth control. The application of beta-adrenoblockers metoprolol and atenolol prevented stimulating effect of norepinephrine. Zofenopril inhibited the growth of cardiomyocytes but enalapril had no effect on this process. The effect of angiotensin I receptor blocker depended on concentration - low concentrations resulted in activation of cardiomyocyte growth; and high concentrations led to the decrease of their growth.

Homocysteine thiolactone was demonstrated to inhibit the growth of 10–12-day-old chicken embryo cardiac tissue explants at 7 × 10−9 −1 × 10−3 M concentrations in a dose-dependent manner. The maximal cardiotoxic effect of homocysteine thiolactone was detected at 1 × 10−3 M, which corresponds to severe hyperhomocysteinemia. The results of experiments on culturing of cardiac tissue explants in the medium containing homocysteine thiolactone (1 × 10−3 M) and ouabain at concentrations regulating the signal-transducing (1 × 10−10 M) and pumping (1 × 10−8 M) functions of Na+,K+ -ATPase indicate that the cardiotoxic effect of homocysteine thiolactone is supposed to result from inhibition of the Na+,K+ -ATPase pumping function.

The Young’s modulus of 10–12-day-old chick embryos’ sensory neurons cultivated in dissociated cell culture was measured using a PeakForce Quantitative Nanomechanical Mapping atomic force microscopy. The native cells were tested in control experiments and after application of ouabain. At low “endogenous” concentration of 10−10 M, ouabain tended to increase the rigidity of sensory neurons. We hypothesize that this trend resulted from activation of Na+,K+-ATPase signal-transducing function.

The technique of atomic force microscopy allows revealing living cell morphology and mechanical properties characterization under physiologically relevant conditions. Here, we review our recent results on living cell reaction to different external influences obtained by this technique. The Bruker PeakForce QNM quasistatic mode was used to study living fibroblasts, erythrocytes, sensory neurons, and endothelial cells.

321 Using whole-cell patch-clamp method, the rat DRG nociceptive neuron membrane was investigated. Extracellular ouabain applications lead to a decrease of the effective charge transfer in the activation gating system of the slow sodium channels (TTX r , Na v 1.8). Ouabain concentration–effective charge transfer (dose– response) dependence has U-like shape after extracellular ouabain application. Left branch of this dependence is monotonous in the range from 100 pM to 1 μ M (K d = 3 nM). Quantum-chemical calculations have shown that the ouabain molecule could effectively form the chelate complex with free calcium ion. As a result, the equilibrium geometry of this complex changes and the probable consequence of this binding is the fact that this complex better fits the transducer site of the Na + ,K + -ATPase. Besides, the chelate complex should specifically activate this transducer site due to the ionionic binding. Less specific free (without calcium) ouabain higher concentration binding takes place at the different Na + ,K + -ATPase site that probably controls its pumping function. Heterogeneity of the ouabain binding sites could explain the U-like shape of the dose– response function under investigation. The inflammatory pain test shows that injections of ouabain at low concentration (i.p., 0.3 mg/kg) lead to pain relief. We hypothesize that physiological role of the endogenous ouabain results in the decrease of nociceptive signals. Mechanisms of Nociceptive Signal Coding: Role of Slow Sodium Channels