The ITFR, impulsive tail flick reflex by short duration nociceptive stimuli

Evaluation of Peripheral Neuropathy in Rat Models of Metabolic Syndrome and Diabetes Mellitus

The dynamics of nephropathy development in rats with type 2 diabetes mellitus, caused by a high-fat diet and the streptozotocin administration (25 mg/kg), and metabolic syndrome, caused by addition of 20% fructose solution to the diet, was evaluated during the experiment. Models with moderate severity of metabolic changes without significant changes in body weight were obtained after 24 weeks. To study neuropathy severity, the method of electroneuromyography was used; the velocities of motor and sensory excitation propagation along the caudal nerve fibers were measured. In modeled diabetes mellitus against the background of hyperglycemia, a marked decrease in motor and sensory propagation rates was observed, and an increase in the response durations was noted from week 12 to week 24, indicating pronounced neuropathy. In the fructose model, the motor response duration increased from week 12, which possibly indicates the development of peripheral neuropathy.

Therapeutic effects of Wharton's jelly-derived Mesenchymal Stromal Cells on behaviors, EEG changes and NGF-1 in rat model of the Parkinson's disease

Human Wharton's jelly-derived Mesenchymal Stromal Cells (hWJ-MSCs) have shown beneficial effects in improving the dopaminergic cells in the Parkinson's disease (PD). In the present study, the effects of hWJ-MSCs on hyperalgesia, anxiety deficiency and Pallidal local electroencephalogram (EEG) impairment, alone and combined with L-dopa, were examined in a rat model of PD. Adult male Wistar rats were divided into five groups: 1) sham, 2) PD, 3) PD + C (Cell therapy), 4) PD + C+D (Drug), and 5) PD + D. PD was induced by injection of 6-OHDA (16 μg/2 μl into medial forebrain bundle (MFB)). PD + C group received hWJ-MSCs (1 × 10⁶ cells, intravenous (i.v.)) twice post PD induction. PD + C+D groups received hWJ-MSCs combined with L-Dopa/Carbidopa, (10/30 mg/kg, intraperitoneally (i.p.)). PD + D group received L-Dopa/Carbidopa alone. Four months later, analgesia, anxiety-like behaviors, were evaluated and Pallidal local EEG was recorded. Level of insulin-like growth factor 1 (IGF-1) was measured in the striatum and dopaminergic neurons were counted in substantia nigra (SNc). According to data, MFB-lesioned rats showed hyperalgesia in tail flick, anxiety-like symptoms in cognitive tests, impairment of electrical power of pallidal local EEG as field potential, count of dopaminergic neurons in SNc and level of IGF-1 in striatum. These complications restored significantly by MSCs treatment (p < 0.001). Our findings confirm that chronic treatment with hWJ-MSC, alone and in combination with L-Dopa, improved nociception and cognitive deficit in PD rats which may be the result of increasing IGF-1 and protect the viability of dopaminergic neurons.

Ketamine induces central antinociception mediated by endogenous cannabinoids and activation of CB1 receptors

The participation of endocannabinoids in central and peripheral antinociception induced by several compounds has been shown by our group. In this study, we investigated the effect of endocannabinoids on the central antinociception induced by ketamine. The nociceptive threshold for thermal stimulation was measured using the tail-flick test in Swiss mice. The drugs were administered intracerebroventricularly. Probabilities less than 5% (p < 0.05) were considered to be statistically significant (Two-way ANOVA/Bonferroni's test). The CB₁-selective cannabinoid receptor antagonist AM251 (2 and 4 μg) completely reversed the central antinociception induced by ketamine (4 μg) in a dose-dependent manner. In contrast, the CB₂-selective cannabinoid receptor antagonist AM630 (2 and 4 μg) did not antagonize this effect. Additionally, the administration of the anandamide amidase inhibitor MAFP (0.2 μg) and anandamide uptake inhibitor VDM11 (4 μg) significantly enhanced the antinociception induced by a low dose of ketamine (2 μg). It was concluded that central antinociception induced by ketamine involves the activation of CB₁ cannabinoid receptors. Mobilization of cannabinoids might be required for the activation of those receptors, since inhibitors of the endogenous cannabinoids potentiate the effect of Ketamine.

Synthesis of novel norsufentanil analogs via a four-component Ugi reaction and in vivo, docking, and QSAR studies of their analgesic activity

Novel substituted amino acid tethered norsufentanil derivatives were synthesized by the four-component Ugi reaction. Norsufentanil was reacted with succinic anhydride to produce the corresponding carboxylic acid. The resulting carboxylic acid has undergone a multicomponent reaction with different aldehydes, amines, and isocyanides to produce a library of the desired compounds. In all cases, amide bond rotation was observed in the NMR spectra. In vivo analgesic activity of the synthesized compounds was evaluated by a tail flick test. Very encouraging results were obtained for a number of the synthesized products. Some of the synthesized compounds such as 5a, 5b, 5h, 5j, and 5r were found to be more potent than sufentanil, sufentanil citrate, and norsufentanil. Binding modes between the compounds and mu and delta-opioid receptors were studied by molecular docking method. The relationship between the molecular structural features and the analgesic activity was investigated by a quantitative structure-activity relationship model. The results of the molecular modeling studies and the in vivo analgesic activity suggested that the majority of the synthesized compounds were more potent than sufentanil and norsufentanil.

Central antinociception induced by ketamine is mediated by endogenous opioids and μ- and δ-opioid receptors

It is generally believed that NMDA receptor antagonism accounts for most of the anesthetic and analgesic effects of ketamine, however, it interacts at multiple sites in the central nervous system, including NMDA and non-NMDA glutamate receptors, nicotinic and muscarinic cholinergic receptors, and adrenergic and opioid receptors. Interestingly, it was shown that at supraspinal sites, ketamine interacts with the μ-opioid system and causes supraspinal antinociception. In this study, we investigated the involvement of endogenous opioids in ketamine-induced central antinociception. The nociceptive threshold for thermal stimulation was measured in Swiss mice using the tail-flick test. The drugs were administered via the intracerebroventricular route. Our results demonstrated that the opioid receptor antagonist naloxone, the μ-opioid receptor antagonist clocinnamox and the δ-opioid receptor antagonist naltrindole, but not the κ-opioid receptor antagonist nor-binaltorphimine, antagonized ketamine-induced central antinociception in a dose-dependent manner. Additionally, the administration of the aminopeptidase inhibitor bestatin significantly enhanced low-dose ketamine-induced central antinociception. These data provide evidence for the involvement of endogenous opioids and μ- and δ-opioid receptors in ketamine-induced central antinociception. In contrast, κ-opioid receptors not appear to be involved in this effect.