Effect of Basic and Acidic Additives on the Separation of Some Basic Drug Enantiomers on Polysaccharide‐Based Chiral Columns With Acetonitrile as Mobile Phase

The separation of enantiomers of 16 basic drugs was studied using polysaccharide‐based chiral selectors and acetonitrile as mobile phase with emphasis on the role of basic and acidic additives on the separation and elution order of enantiomers. Out of the studied chiral selectors, amylose phenylcarbamate‐based ones more often showed a chiral recognition ability compared to cellulose phenylcarbamate derivatives. An interesting effect was observed with formic acid as additive on enantiomer resolution and enantiomer elution order for some basic drugs. Thus, for instance, the enantioseparation of several β‐blockers (atenolol, sotalol, toliprolol) improved not only by the addition of a more conventional basic additive to the mobile phase, but also by the addition of an acidic additive. Moreover, an opposite elution order of enantiomers was observed depending on the nature of the additive (basic or acidic) in the mobile phase. Chirality 27:228–234, 2015. © 2015 Wiley Periodicals, Inc.     

Dual modulation of CNS voltage-gated calcium channels by cannabinoids: Focus on CB1 receptor-independent effects

The neuromodulatory effects of cannabinoids in the central nervous system have mainly been associated with G-protein coupled cannabinoid receptor (CB1R) mediated inhibition of voltage-gated calcium channels (VGCCs). Numerous studies show, however, that cannabinoids can also modulate VGCCs independent of CB1R activation. Nevertheless, despite the fact that endocannabinoids have a nearly equal efficacy for direct and CB1R-mediated effects on VGCC, the role of the direct cannabinoid–VGCC interaction has been largely underestimated.In this review, we summarize recent studies on the modulation of different types of VGCCs by cannabinoids, highlight the evidence for and implications of the CB1R-independent modulation, and put forward the concept, that direct interaction of cannabinoids and VGCCs is as important in regulation of VGCCs function as the CB1R-mediated effects.     

Effect of a non-hydrolyzable analog of diadenosine polyphosphates on NMDA-mediated currents in isolated pyramidal neurons of the rat hippocampus

Using a patch-clamp technique under voltage clamp conditions, we studied the effect of a non-hydrolyzable analog of diadenosine polyphosphates (AppCH₂ppAs) on chemoactivated transmembrane currents through NMDA channels (NMDA currents) in isolated pyramidal neurons of the rat hippocampal CA3 zone. In 55.7% of the cases, AppCH₂ppAs caused an increase in the peak amplitude of the currents induced by application of aspartate. In 39.5% of the cases, the agent exerted no effect, while in 4.8% these currents were suppressed. When studying the pharmacological effect of an increase in the amplitude of NMDA currents, we found that potentiation of these currents is mediated, first of all, by activation of P₂ purinoceptors and is prevented by a blocker of tyrosine kinases, genistein. Receptor-channel NMDA complexes, due to their ability to be blocked by divalent cations, also contribute to the above effect of AppCH₂ppA. Based on the data obtained, we conclude that AppCH₂ppA influences NMDA receptors via activation of the P₂ receptors and subsequent activation of tyrosine kinases; this leads to the modification of receptor-channel NMDA complexes and to the removal of their tonic blocking by zinc ions. Neirofiziologiya/Neurophysiology, Vol. 38, No. 3, pp. 205–210, May–June, 2006.     

Galactose specific lectins from prostate tissue with different pathologies: biochemical and cellular studies

Background

Galectins—galactose-specific lectins are involved in various types of cell activities, including apoptosis, cell cycle regulation, inflammation and cell transformation. Galectins are implicated in prostate malignat transformation. It is not known yet if prostate glands with different grade of pathologies are expressing different galectins and if these galectins express different effects on the cell viability.

Methods

Cytosolic galactose-spesific lectin fractions from prostate tissue with different diagnosis were purified by affinity chromatography and analyzed by electrophoresis in polyacrylamide gel electrophoresis with sodium dodecyl sulphate. The lectin effects in a source-dependent maner were studied on cell viability on peripheral lymphocytes by MTT reduction method and on apoptosis by flow cytometry method.

Results

Affinity purified galactose-specific lectins fractions from normal and pathological tissue samples are characterized with different protein composition and they express different effects on cell viability and apoptosis.

Conclusion

The effects of cytosolic galactose-specific lectins depend on the source of lectin fraction (glandular tissue disease). We suppose that the released cytosolic galectins from prostatic high grade intraepithelial neoplasia and adenocarcinoma tissue could suppress the immune status of the host patients.

     

Glutamate Postsynaptic Receptors under the Cap: Strictly Limited Access to Receptors in the Postsynaptic Density by Non-Synaptically Released Glutamate

Astroglia is capable of releasing glutamate (Glu) in concentrations sufficient to activate ionotropic Glu receptors. Provided the released Glu reaches the receptors in the postsynaptic density, it can desensitize them. We have tested this possibility in the hippocampal CA1 synapses of rats either by applying exogenous Glu to the CA1 neurons or activating Glu release by astroglia. We found that Glu does not reach the synapses due to the existence of a protective uptake cap, which is sensitive to dihydrokainate, an inhibitor of GLT-type Glu transporter(s). Our results suggest that extrasynaptic and postsynaptic densities of the membranes of CA1 neurons form separate compartments differing from each other in the mechanisms and efficiency of processing external Glu. This provides additional diversity to specialized regulation of synaptic transmission and electrical excitation of pyramidal neurons.     

Effects of Long-Term Hypoxia/Hypoglycemia on Synaptic Transmission between the CA3 and CA1 Zones in Rat Hippocampal Slices

On rat hippocampal slices using a standard patch-clamp technique in the whole-cell configuration, we studied the effects of long-term (40 to 60 min) hypoxia/hypoglycemia (HH) on excitatory postsynaptic currents (EPSC) evoked by stimulation of Schaffer collaterals in the cells of the CA1 zone. In addition to the earlier described effect of an immediate drop in the EPSC amplitude, a significant transient increase in its amplitude 30-50 min after the beginning of HH was observed. A pharmacologically isolated NMDA component of excitatory synaptic events underwent similar changes: 30-50 min after the blockade of NMDA receptor-mediated current, a fast recovery of its amplitude to the control (or even higher) values occurred. A blocker of NMDA/glutamate (Glu) receptors, D-aminophosphonovaleric acid (D-APV), and a competitive nonspecific antagonist of metabotropic Glu receptors, (RS)--methyl-4-carboxyphenylglycine – (RS)-MCPG – did not influence the HH-induced initial suppression of synaptic transmission but completely eliminated its delayed recovery. Our findings allow us to suppose that NMDA receptors, as well as metabotropic Glu receptors, play important roles in the cascade of biochemical reactions resulting in death of hippocampal pyramidal cells in the course of and after long-term ischemia in vivo.     

Effects of mibefradil on synaptic transmission in the hippocampus and on voltage-dependent currents in isolated hippocampal and thalamic neurons of the rat

The effects of a novel anti-hypertensive drug, mibefradil, on voltage-dependent currents in isolated thalamic and hippocampal neurons, as well as on synaptic transmission in the hippocampus have been studied. Mibefradil exerted a potent inhibitory action on low-threshold calcium currents in thalamic neurons (IC₅₀=160 nM). In higher concentrations (1–20 μM), this drug blocked not only low-threshold calcium current but also voltage-dependent sodium and delayed potassium currents in pyramidal hippocampal neurons. The amplitude of population action potentials in hippocampal slices decreased by 55% in the presence of 20μM mibefradil. All of the effects of mibefradil were almost completely reversible. In our experiments, the sensitivity of low-threshold calcium channels in thalamic neurons to mibefradil was higher than that observed on other objects. The ability of mibefradil to block not only calcium currents but also other types of voltage-dependent ion conductances in hippocampal neurons may be considered an essential factor that determines the specificity of the pharmacological profile of this drug.