Neuroprotective effects of the CTK 01512-2 toxin against neurotoxicity induced by 3-nitropropionic acid in rats.

The mitochondrial inhibitor 3-nitropropionic acid (3-NP) induces excitotoxicity. The authors hypothesized that CTK 01512-2, a recombinant peptide calcium channel N-type blocker, and the TRPA1 antagonist, could show neuroprotective effects. The male Wistar rats received 3-NP [25 mg/kg (i.p.) for 7 days], and a treatment of CTK 01512-2 was delivered intrathecally (i.t.), thrice a week. The neuroprotective effects were evaluated by [18F]FDG MicroPET analysis. The CTK 01512-2 toxin was able to reestablish similar glucose uptakes on the control animals. To detect the neurobehavioral effects from 3-NP, three protocols (6.25, 12.5, 18.75 mg/kg of 3-NP (i.p.), for 3, 4, and 6 days, respectively) were evaluated by performance tests (open field test, walk footprint, elevated plus-maze, Y-maze, and the object recognition test). Important disabilities in the gait of the rats were seen, as well as memory deficits, and anxious behavior in the animals that were treated with all 3-NP protocols. The dose of 18.75 mg/kg (for 3 days) showed the most pronounced behavioral effects and lethality, while the rats treated with 12.5 mg/kg (for 4 days) showed behavioral effects similar to the 6.25 mg/kg dose (for 6 days). The third protocol was then repeated and the rats were treated with the CTK 01512-2 toxin to be evaluated behaviorally again. The recombinant peptide prevented all of the gait-evaluated parameters that were induced by 3-NP at a 6.25 mg/kg dose, which displayed an improvement in the exploratory activities. Overall, these results have reinforced the positive effects of CTK 01512-2 against the behavioral changes that were induced by the mitochondrial inhibitor 3-NP.

Phoneutria nigriventer Tx3-3 peptide toxin reduces fibromyalgia symptoms in mice.

Fibromyalgia is characterized by the amplification of central nervous system pain with concomitant fatigue, sleep, mood disorders, depression, and anxiety. It needs extensive pharmacological therapy. In the present study, Swiss mice were treated with reserpine (0.25 mg/kg, s.c.) over three consecutive days, in order to reproduce the pathogenic process of fibromyalgia. On day 4, the administrations of the Tx3-3 toxin produced significant antinociception in the mechanical allodynia (87.16% ±12.7%) and thermal hyperalgesia (49.46% ± 10.6%) tests when compared with the PBS group. The effects produced by the classical analgesics (duloxetine 30 mg/kg, pramipexole 1 mg/kg, and pregabalin 30 mg/kg, p.o., respectively) in both of the tests also demonstrated antinociception. The administrations were able to increase the levels of the biogenic amines (5-HTP and DE) in the brain. The treatments with pramipexole and pregabalin, but not duloxetine, decreased the immobility time in the FM-induced animals that were submitted to the forced swimming test; however, the Tx3-3 toxin (87.45% ± 4.3%) showed better results. Taken together, the data has provided novel evidence of the ability of the Tx3-3 toxin to reduce painful and depressive symptoms, indicating that it may have significant potential in the treatment of FM.

Application of the UV-vis spectrophotometry method for the determination of glutamate in the cerebrospinal fluid of rats.

In experimental nociception models, there is an increase in the glutamate cerebrospinal fluid (CSF) and a decrease in its levels in analgesic treatments. For the determination of glutamate in CSF, an analytical UV spectrophotometric method was developed and validated. The measurements on the UV-vis spectrophotometer were performed after the derivatization reaction of the neurotransmitter, when reading in the ultraviolet (UV) region, at the maximum absorption wavelength of 265 nm. The technique presented excellent linearity, as well as good intraday and interday precision, with coefficients of variation less than 15 %, and a correlation coefficient close to 1.0 (lower dispersion of the experimental set points and lower uncertainty of the estimated regression coefficients). The analytical conditions that were established by the ultraviolet spectrophotometric method demonstrated selectivity, linearity, precision, specificity, robustness, and accuracy. This is suitable for the quantitative determination of glutamate in the CSF. The technique developed by UV-vis spectrophotometry for glutamate dosing was fast, efficient, easy to perform, and more economically accessible when compared to current standard techniques. When comparing the data obtained in this study with the results of the official methodology, in which HPLC and spectrofluorimetry were used, it was observed that the closest values of glutamate release occurred between the spectrofluorimeter and the UV-vis spectrophotometer. The UV-vis spectrophotometry method for the determination of CSF glutamate has been shown to be accurate, reproducible, and satisfactory, making it an extremely advantageous and a viable alternative for the determination of amino acid glutamate.

Antinociceptive and genotoxic assessments of the antagonist TRPV1 receptor SB-366791 on morphine-induced tolerance in mice.

Chronic pain is mainly treated with opioid analgesics such as morphine. However, the use of these substances can cause adverse effects, including dependence and tolerance, necessitating the discovery of a new approach to analgesic therapies. The transient receptor potential vanilloid 1 (TRPV1) is linked to thermal sensibility and has been considered as a new therapeutic option for pain treatment. This study aims to investigate the antinociceptive effect and toxicity of SB-366791, a TRPV1 antagonist. Morphine-tolerant and morphine non-tolerant Swiss mice were submitted to the hot plate and thermal tail flick tests. Toxicological evaluations of the genotoxic and mutagenic activities of SB-366791 were assessed using a comet assay and micronucleus test, and the Salmonella/microsome mutagenicity assay. In the hot plate test, intrathecal injection of SB-366791 or morphine resulted in significantly increased antinociception in non-tolerant mice. SB-366791 also led to an analgesic effect in the tail flick test. Tolerant mice that received SB-366791 demonstrated a central antinociceptive effect in both thermal tests. No genotoxic effects were observed in the comet assay and no mutagenic effects were detected in the micronucleus test or in the Salmonella/microsome assay. Behavioral results of the thermal nociception tests show that SB-366791 has antinociceptive potential in both morphine-tolerant and non-tolerant mice and does not cause genotoxic or mutagenic effects. Nevertheless, new studies should be performed to clarify the activity and participation of vanilloid channels in the antinociception of SB-366791.