Comparative investigation of analgesic tolerance to taurine, sodium salicylate and morphine: Involvement of peripheral muscarinic receptors.

Nowadays various analgesic medications are used for the management of acute and chronic pain. Among these opioid and non-steroidal anti-inflammatory drugs stand in the first line of therapy, however, prolonged administration of these substance is generally challenged by development of analgesic tolerance in patients. Therefore, it is highly valuable to find new pharmacological strategies for prolonged therapeutic procedures. In this respect, Taurine, a free amino acid, has been shown to induce significant analgesia at both spinal and peripheral levels through cholinergic mechanisms. In the present study, we used hot-plate analgesic test to investigate how taurine either as a single medication or in combination with sodium salicylate and morphine may affect both acute response to pain and development of analgesic tolerance. The effect of taurine was also tested on morphine withdrawal syndrome. Hyoscine butyl bromide was used to assess the role of muscarinic receptors in taurine-mediated effects. Finally, biochemical assay was done to reveal how the activity of brain acetylcholinesterase may change in relation with muscarinic receptor activity. Results indicated that acute administration of taurine-sodium salicylate combination causes more potent analgesia compared to the use of tau (but not SS alone) and this seems to be mediated via activity of muscarinic receptors in peripheral nervous system. Furthermore, the effect of this combination undergoes less analgesic tolerance during time. Combination of taurine and morphine is an effective strategy to attenuate both morphine analgesic tolerance and dependence and this also seems to depend on activity of muscarinic receptors, however through differential cellular mechanisms.

Copper concentration in multiple sclerosis: a systematic review and meta-analysis.

BACKGROUND: A wide range of risk factors, from genetic to environmental, have been identified to play role in the etiology of multiple sclerosis. However, the role of trace element remains mostly unknown. We sought to combine all available evidence to assess the association between copper concentration and multiple sclerosis. METHODS: This systematic review and meta-analysis was conducted based on PRISMA guidelines. PubMed, Scopus, Embase, and Web of Science were searched since inception till July 2020. Observational studies that assessed copper as exposure in serum, plasma, whole blood, and cerebrospinal fluid were included. Standardized mean differences (SMD), comparing the mean of copper concentration in multiple sclerosis patients versus healthy controls, were considered as the measure of association. The fixed-effect model with inverse variance weighting was used to combine the findings. RESULTS: Twenty studies inclusive of 797 multiple sclerosis cases and 875 healthy controls were included in the meta-analysis (all case-control studies). The combined SMDs were 1.25 (95% confidence interval [CI] 0.95 to 1.55, number of included studies [n]=4) in plasma, 0.45 (CI 0.22 to 0.68, n=4) in whole blood, 0.19 (CI 0.06 to 0.33, n=12) in blood serum and 1.23 (CI 0.83 to 1.64, n=4) in cerebrospinal fluid. CONCLUSIONS: We found a higher concentration of copper in multiple sclerosis patients than healthy controls. The possible causal nature of the observed associations warrants further investigation with prospective data.

Prolonged hyperoxia preconditioning attenuates behavioral symptoms of 6-hydroxydopamine-induced Parkinsonism.

OBJECTIVES: Several lines of evidences show that hyperoxia preconditioning provides neuronal protection against central nervous system ischemic damages. Common pathways including mitochondrial dysfunction, apoptosis, and caspase activation are involved in acute neurodegeneration (e.g. after cerebral ischemia) and chronic neurodegeneration (e.g. neuronal death in Parkinson's disease). The aim of the present research was to study the effect of hyperoxia preconditioning on 6-hydroxydopamine (6-OHDA)-induced Parkinsonism. METHODS: Male Wistar rats were first subjected to either air with high oxygen concentration (>90%) or atmospheric air for prolonged (24 hours) or intermittent (six consecutive days, 4 hours each day) periods and then 6-OHDA was injected into their left striatums by stereotaxic surgery. Development and severity of the 6-OHDA-induced Parkinsonism was assessed using apomorphine-induced rotational test, elevated body swing test, and rotarod test within 2-5 weeks after the surgery. RESULTS: Significant data obtained in rats treated with prolonged hyperoxia, but not the intermittent hyperoxia. In these rats, the number of apomorphine-induced rotations was ∼60% lower than that in control and sham groups. Rats belonging to the prolonged hyperoxia group also showed considerably better motor performance and learning pattern in rotarod test. These results were confirmed by the data obtained in the elevated body swing test. DISCUSSION: Our findings show that the prolonged hyperoxia preconditioning attenuates the behavioral symptoms of 6-OHDA-induced Parkinsonism. Considering the well-known correlation between dopaminergic neuronal death in the substantia nigra and the behavioral symptoms of 6-OHDA-induced Parkinsonism, it could be speculated that the prolonged hyperoxia preconditioning induces the mechanisms that provide dopaminergic neuroprotection against Parkinsonism-induced toxins.