Antagonists D1 and D2 of Dopamine Receptors Determine Different Mechanisms of Neuroprotective Action in the Frog Vestibular.

The high functional plasticity of the glutamatergic synapse of the vestibular epithelium is supported by a delicate balance of excitatory and inhibitory interactions. One of the peptides co-localized with acetylcholine (ACh) in the efferent fibers is dopamine. Using external perfusion of the synaptic zone and multiunit recording of an afferent fibers activity the effect of dopamine antagonists on the background firing rate of the semicircular canal sensory fibers was studied on the isolated frog vestibular. The present research revealed that the dopamine receptor antagonist (D1) SCH-23390 significantly reduced the level of background activity at high concentrations. In contrast, D2 antagonist eticlopride caused positive-negative answer of the background activity of the sensory fibers in dose-depending manner. The data confirm the hypothesis that dopamine, being tonic released from the efferent fibers, realizes neuroprotective inhibitory control over the afferent glutamatergic synapse activity in the vestibular epithelium via D1 and D2 receptors.

Neuroleptic Chlorpromazine Modulates Ca2+ Responses in Macrophages.

Using Fura-2AM microfluorimetry, we have shown for the first time that sigma-1 receptor antagonist neuroleptic chlorpromazine significantly inhibits glutoxim- and molixan-induced Ca2+ responses and Ca2+ responses induced by endoplasmic reticulum Са2+-ATPase inhibitors thapsigargin and cyclopiazonic acid in rat peritoneal macrophages. The results suggest the involvement of sigma-1 receptors in the signaling cascade induced by glutoxim or molixan and leading to intracellular Ca2+ concentration increase and in the regulation of store-dependent Ca2+ entry in macrophages.

Sigma-1 Receptor Agonist Amitriptyline Inhibits Store-Dependent Ca2+ Entry in Macrophages.

Using Fura-2AM microfluorimetry, we have shown for the first time that sigma-1 receptor agonist-tricyclic antidepressant amitriptyline-significantly inhibits store-dependent Ca2+ entry, induced by endoplasmic Ca2+-ATPase inhibitors thapsigargin and cyclopiazonic acid, in rat peritoneal macrophages. The results suggest a possible involvement of sigma-1 receptors in the regulation of store-dependent Ca2+ entry in macrophages.

Sigma-1 Receptor Antagonists Haloperidol and Chlorpromazine Modulate the Effect of Glutoxim on Na+ Transport in Frog Skin.

Using voltage-clamp technique, the involvement of sigma-1 receptors in the regulation of Na+ transport in frog skin by the immunomodulatory drug glutoxim was investigated. We have shown for the first time that preincubation of the frog skin with the sigma-1 receptor antagonists haloperidol and chlorpromazine attenuates the stimulatory effect of glutoxim on the Na+ transport. The results suggest the possible involvement of the sigma-1 receptors in the regulation of Na+ transport in frog skin epithelium by glutoxim.

Amitriptyline Attenuates Ca2+ Responses Induced by Glutoxim and Molixan in Macrophages.

Using Fura-2AM microfluorimetry, we have shown for the first time that sigma-1 receptor agonist, tricyclic antidepressant amitriptyline, significantly inhibits glutoxim- and molixan-induced Ca2+-responses in rat peritoneal macrophages. The results suggest possible involvement of sigma-1 receptors in the signaling cascade induced by glutoxim or molixan and leading to intracellular Ca2+ concentration increase in macrophages.

The Effects of Weak Static Magnetic Field on the Development of Organotypic Tissue Culture in Rats.

The effects of weak static magnetic field on the organotypic tissue culture of the rat cerebral cortex, liver, and spleen have been investigated. Exposure to a 200 µT static magnetic field induces tissue development, leading to the intensification of regeneration processes compared to the control explants.

Soluble Guanylate Cyclase As the Key Enzyme in the Modulating Effect of NO on Metabotropic Glutamate Receptors.

The synaptic plasticity of the afferent synapse of the vestibular apparatus is defined by the dynamic interaction of ionotropic and metabotropic glutamate receptors and the modulators of synaptic transmission. It was shown that nitric oxide modulates iGluR responses. In this paper, the effect of NO on the function of the afferent synapse mGluR was investigated. Inhibitor of nitric oxide synthase lowered the level of background activity but increased the amplitude of the responses of groups I and II mGluR agonist ACPD. Donor NO SNAP increased the level of background activity. Short-term perfusion of the synaptic region with low concentrations of SNAP led to a decrease in the amplitude of the answers of mGluR agonists ACPD and DHPG. The inhibitory effect of the NO donor was eliminated under blockade of soluble guanylate cyclase with a specific inhibitor ODQ. A prolonged application of NO did not cause a statistically significant change in the amplitude of the ACPD response. However, SNAP at concentrations of 10 and 100 µM increased the amplitude of the mGluR agonist responses 30 and 15 minutes, respectively, after termination of the NO donor exposure. The obtained data show the multidirectional effect of NO on the function of mGluR and testify to the existence of a complex modulating mechanism of the afferent flow from vestibular organs to the central nervous system.

Epoxygenase Inhibitors Attenuate the Stimulatory Effect of Glutoxim on Na+ Transport in Frog Skin.

Using voltage-clamp technique, the involvement of epoxygenases in immunomodulatory drug glutoxim regulation of Na+ transport in frog skin was investigated. We have shown for the first time that preincubation of the frog skin with epoxygenase inhibitors econazole or proadifen almost completely inhibits the stimulatory effect of glutoxim on Na+ transport. The data suggest the involvement of the enzymes and/or products of epoxygenase oxidation pathway of arachidonic acid metabolism in glutoxim effect on Na+ transport in frog skin epithelium.

Sigma-1 Receptor Antagonist Haloperidol Attenuates Store-Dependent Ca2+ Entry in Macrophages.

Using Fura-2AM microfluorimetry, we have shown for the first time that preincubation of macrophages with sigma-1 receptor antagonist haloperidol leads to a significant inhibition of the store-dependent Ca2+ entry induced by endoplasmic Ca2+-ATPase inhibitors thapsigargin or cyclopiazonic acid in rat peritoneal macrophages. The results suggest the involvement of the sigma-1 receptor in the regulation of storedependent Ca2+ entry in macrophages.

Mechanism of Activation of Enteric Nociceptive Neurons via Interaction of TLR4 and TRPV1 Receptors.

Evidence obtained by immunohistochemical double labeling and confocal laser scanning microscopy suggests that capsaicin, a ligand of the TRPV1 nociceptive vanilloid receptor, increases the number of TLR4-positive neurons in the rat colon myenteric plexus. In colitis caused by trinitrobenzene sulfonate, an increase in TRPV1 expression was more significant in both plexuses. Specific inhibitor of the TLR4 (C34) pattern-recognition receptor reduces TRPV1 expression in enteric neurons of both intact rats and rats with induced acute colitis. Thus, stimulation of nociceptive neurons by means of direct activation of their receptors of innate immunity (TLR4) is one of the possible mechanisms underlying the visceral pain in bacterial invasion and inflammatory bowel diseases.

Phospholipase A2 Inhibitors Modulate the Effect of Trifluoperazine on the Intracellular Ca2+ Concentration in Macrophages.

Using Fura-2AM microfluorimetry, it was shown for the first time that phospholipase A2 inhibitors 4-bromophenacyl bromide and glucocorticosteroids prednisolone and dexamethasone attenuate Ca2+ responses induced by neuroleptic trifluoperazine in macrophages. The results suggest the involvement of phospholipase A2 and arachidonic acid metabolism cascade in the effect of trifluoperazine on intracellular Ca2+ concentration in macrophages.

Trifluoperazine Attenuates Store-Dependent Ca2+ Entry in Macrophages.

Using Fura-2AM microfluorimetry, we have shown for the first time that preincubation of macrophages with the calsequestrin inhibitor neuroleptic trifluoperazine leads to a significant inhibition of the store-dependent Ca2+ entry induced by endoplasmic Ca2+-ATPase inhibitors thapsigargin or cyclopiazonic acid in rat peritoneal macrophages. The results suggest calsequestrin involvement in the regulation of the store-dependent Ca2+ entry in macrophages.

Sympathetic Innervation of Stomach in Postnatal Development.

Sympathetic innervation of the stomach was studied in rats by the method of retrograde axon transport of Fast Blue in postnatal ontogenesis. The number of labeled neurons increased in the first 10 days of life and then did not change until the senescence. All labeled neurons innervating the stomach contain the catecholamine synthesis enzyme, tyrosine hydroxylase. The proportion of labeled neuropeptide Y-immunopositive neurons did not change in the development, the percentage of labeled calbindin-immunoreactive neurons decreased in the first month of life.

[Age-development changes of the sympathetic innervation of the rat stomach.]

Sympathetic innervation of the stomach is carried out by the prevertebral ganglia of the solar plexus. The localization and neurochemical composition of neurons innervating the stomach in postnatal ontogenesis in rats was studied using the method of retrograde axon transport of Fast Blue. In all animals, the celiac ganglia had more labeled neurons compared to the superior mesenteric ganglion. The number of labeled neurons increased in the first 10 days of life and then did not change until the senescence. All labeled neurons innervating the stomach contain the catecholamine synthesis enzyme, tyrosine hydroxylase. The proportion of labeled neuropeptide Y-immunopositive neurons did not change in the development, the percentage of labeled calbindin-immunoreactive neurons decreased in the first month of life.

[Developmental changes of neurotransmitter properties in sympathetic neurons].

Neurochemical composition of metasympathetic nervous system is characterized by a large variation. The main part of the intramural ganglionic neurons is cholinergic. Along with cholinergic neurons, there are ganglionic neurons containing serotonin, histamine, GABA, and several peptides: cholecystokinin, dynorphin, enkephalin, galanin, gastrin-releasing peptide (bombesin in mammals), neuropeptide Y, neurotensin, somatostatin, tachykinins, neurokinin A, vasoactive intestinal polypeptide and calcitonin gene related peptide. Gases as NO, CO, H2S, also act as neurotransmitters. Separate groups of neurons differ in the content of neuronal calcium-binding proteins, such as calbindin, calretinin and parvalbumin and neurofilaments: low molecular weight, a medium molecular weight and high molecular weight. Neurons of the enteric ganglia are the most different by their neurochemistry. There is a species difference in the ganglia of large animals and humans there are more combinations of chemical transmitters. Synthesis of neurotransmitters takes place even in the embryonic period and by the time of birth the most of neurons contain acetylcholine. In postnatal ontogenesis, the proportion of neurons expressing the NO-synthase decreases in the enteric and cardiac intramural ganglionic neurons. The functional significance of these changes is unclear.

Lipoxygenases modulate the effect of glutoxim on Na+ transport in the frog skin epithelium.

Using voltage-clamp technique, the involvement of lipoxygenases in the effect of immunomodulatory drug glutoxim on Na+ transport in frog skin was investigated. It was shown for the first time that preincubation of the skin with lipoxygenase inhibitors caffeic acid, baicalein, and nordihydroguaiaretic acid significantly decreases the stimulatory effect of glutoxim on Na+ transport. The data suggest the involvement of lipoxygenase oxidation pathway of arachidonic acid metabolism in the glutoxim effect on Na+ transport in frog skin epithelium.

The effect of chlorpromazine on intracellular Ca2+ concentration in macrophages.

Using Fura-2AM microfluorimetry, it was shown for the first time that neuroleptic chlorpromazine causes intracellular Ca2+ concentration increase in macrophages due to Ca2+ mobilization from intracellular Ca2+ stores and subsequent Ca2+ entry from the external medium. Chlorpromazine-induced Ca2+ entry is inhibited by La3+ and 2-aminoethoxydiphenyl borate and is associated with Ca2+ store depletion.

Antinociceptive effect of the agonist of 5-HT1A receptors buspirone in the model of abdominal pain in dogs.

We have demonstrated that activation of 5-HT1A receptors with buspirone promotes visceral analgesia in awake dogs. The administration of 0.035 mg/kg (i.m.) of the drug caused depression of viscero-motor (contraction of the abdominal muscles) and pressor (increase in the heart rate) responses to noxious distension of the large intestine. An increase in the dose to 0.07 and 0.14 mg/kg did not enhance the antinociceptive effect of buspirone but triggered basal tachycardia. The obtained results provide evidence of the inhibitory role of 5-HT1A receptors in modulating visceral pain sensitivity and the possibility of an exciting effect of their activation on the cardiovascular system.

Methyl-ß-cyclodextrin modulates thapsigargin-induced store-dependent Ca2+ entry in macrophages.

Using Fura-2AM microfluorimetry, we have shown for the first time that preincubation of macrophages with methyl-ß-cyclodextrin, inducing cholesterol extraction from membranes and raft disruption, leads to significant inhibition of thapsigargin-induced store-dependent Ca2+ entry in rat peritoneal macrophages. In contrast, macrophage treatment with methyl-ß-cyclodextrin after Ca2+ entry mechanisms were activated by store depletion by thapsigargin application leads to potentiation of subsequent store-dependent Ca2+ entry. The results suggest that intact lipid rafts are necessary for the activation but not the maintenance of store-dependent Ca2+ entry in macrophages.

Possible mechanism of bursting suppression in nociceptive neurons.

The use of the mathematical model of rat nociceptive neuron membrane allowed us to predict a new mechanism of suppression of ectopic bursting discharges, which arise in neurons of dorsal root ganglia and are one of the causes of neuropathic pain. The treatment with comenic acid leads to switching off the ectopic bursting discharges due to a decrease in the effective charge transferring via the activation gating structure of the slow sodium channels (Na V1.8a). Comenic acid is a drug substance of a new non-opioid analgesic [1] Thus, this analgesic not only reduces the frequency of rhythmic discharges of nociceptive neuron membrane [2] but also it suppresses its ectopic bursting discharges.