Impact of a Newly Synthesized Molecule (2-chloro-N-(1-(3,4-dimethoxyphenyl) propan-2-yl)-2-phenylacetamide) on the Bioelectrogenesis and the Contractile Activity of Isolated Smooth Muscles

Introduction: Examination of the potential possibilities of 2-chloro-N-(1-(3,4-dimethoxyphenyl)propan-2-yl)-2-phenylacetamide (IQP) to affect bioelectrogenesis and the contractile activity of isolated smooth muscles (SM) from stomach. Aim: Having in mind the structural similarities between the molecules of papaverine and IQP, the aim of the present study was to examine such features of the newly synthesized molecule that may potentially affect the muscle tonus, spontaneous bioelectrical and contractile activities of smooth muscles isolated from the stomach, basing on specific mechanisms of papaverine. Materials and methods: The synthesis of IQP is based on the initially formed aziridine ring by principles of Gilbert’s reaction. Impact of IQP on the bioelectrogenesis and the contractile activity of isolated smooth muscles from male Wistar rats was measured by the single sucrose-gap method and isometrically recorded. Results: IQP (1×10-5 – 2.5×10-4 mol/l) causes muscle relaxation, producing changes in two processes that have influence on the mechanical activity of smooth muscles:1.    Blocked Ca2+ influx through the potential-dependent membrane Ca2+ channels, followed in turn by lowering the Ca2+ intracellular levels. This effect is proved by the changes in the frequency and amplitude of spike-potentials in sucrose-bridge experiments when IQP is applied.2.    Activation of a cAMP-dependent signal cascade. The relaxing effect of IQP was significantly reduced in the presence of KT5720(5×10-6 mol/l), an inhibitor of protein kinase A. Conclusion: We assume that there might be interconnections between these two IQP-dependent processes, because PKA-dependent phosphorylation of the L-type Ca2+ channels in smooth muscles provokes a reaction of inactivation.

Bioassay-Guided Evaluation of Antinociceptive Effect ofN-Salicyloyltryptamine: A Behavioral and Electrophysiological Approach

We investigated the antinociceptive and nerve excitability effects of theN-salicyloyltryptamine (NST) NST-treated mice exhibited a significant decrease in the number of writhes when 100 and 200 mg/kg (i.p.) were administered (i.p.). This effect was not antagonized by naloxone (1.5 mg/kg, i.p.). NST inhibited the licking response of the injected paw when 100 and 200 mg/kg were administered (i.p.) to mice in the first and second phases of the formalin test. Because the antinociceptive effects could be associated with neuronal excitability inhibition, we performed the single sucrose gap technique and showed that NST (3.57 mM) significantly reduced (29.2%) amplitude of the compound action potential (CAP) suggesting a sodium channel effect induced by NST. Our results demonstrated an antinociceptive activity of the NST that could be, at least in part, associated to the reduction of the action potential amplitude. NST might represent an important tool for pain management.

Conduction Deficits and Membrane Disruption of Spinal Cord Axons as a Function of Magnitude and Rate of Strain

White matter strips extracted from adult guinea pig spinal cords were subjected to tensile strain (stretch) injury ex vivo. Strain was carried out at three magnitudes (25, 50, and 100%) and two strain rate regimens: slow (0.006–0.008 s−1) and fast (355–519 s−1). The cord samples were monitored physiologically using a double sucrose-gap technique and anatomically using a horseradish peroxidase assay. It seems that a higher magnitude of strain inflicted significantly more functional and structural damage within each strain rate group. Likewise, a higher strain rate inflicted more damage when the strain magnitude was maintained. It is evident that axons have remarkable tolerance to strain injury at a slow strain rate. Even a 100% strain at the slow rate only eliminated two-thirds of the compound action potential amplitude and resulted in almost no membrane damage when examined 30 min after strain. It is also clear that the spontaneous recovery is evident yet not complete compared with preinjury levels at the fast strain rate. To examine the factors that might influence the vulnerability of axons to strain, we have shown that the axonal diameters did not play a significant role in dictating the susceptibility of axons to strain. Rather, it is speculated that the location of axons might be a more important factor in this regard. The knowledge gained from this study is likely to be informative in elucidating the spinal cord biomechanical response to strain and strain rate.

Effect of sodium nitroprusside on parameters of electrical and contractile activities of lower esophageal sphincter unstriped muscles

Investigations of electrical and contractile activities of lower esophageal sphincter unstriped muscles under sodium nitroprusside impact have been fulfilled by the method of double sucrose gap. Effect of nitric oxide donor on potassium and calcium membrane conductance has been evaluated, as well as the role of intracellular NO-synthase. Membrane hyperpolarization and contractile activity decrease during the use of sodium nitroprusside and L-NAME have been observed. Conclusion has been drawn of NO effect on potassium membrane conductance as well as of the possible effect on contractile proteins and activation of cAMP-dependent regulation of LES UM physiological functions.

Control of Membrane Sealing in Injured Mammalian Spinal Cord Axons

The process of sealing of damaged axons was examined in isolated strips of white matter from guinea pig spinal cord by recording the “compound membrane potential,” using a sucrose-gap technique, and by examining uptake of horseradish peroxidase (HRP). Following axonal transection, exponential recovery of membrane potential occurred with a time constant of 20 ± 5 min, at 37°C, and extracellular calcium activity ([Ca2+]o) of 2 mM. Most axons excluded HRP by 30 min following transection. The rate of sealing was reduced by lowering calcium and was effectively blocked at [Ca2+]o ≤ 0.5 mM, under which condition most axons continued to take up HRP for more than 1 h. Sealing at higher [Ca2+]o was blocked by calpain inhibitors (calpeptin and calpain inhibitor-1) indicating a requirement for type II (mM) calpain in the sealing process. Following compression injury, the amplitude of the maximal compound action potential conducted through the injury site was reduced. The extent of amplitude reduction was increased when the tract was superfused with calcium-free Krebs' solution (Ca2+ replaced by Mg2+). These results suggest that the fall in [Ca2+]o seen following injury in vivo is sufficient to prevent membrane sealing and may paradoxically contribute to axonal dieback, retrograde cell death, and “secondary” axonal disruption.