Neuroscience letters
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Neuroscience letters · Jun 2014
Co-administration of memantine with epinephrine produces a marked peripheral action in intensifying and prolonging analgesia in response to local skin pinprick in rats.
The purpose of this study was to examine the effect of epinephrine as adjuvant for memantine or lidocaine as an infiltrative anesthetic. Using a rat model of cutaneous trunci muscle reflex (CTMR), we evaluated the effects of adding epinephrine to memantine or lidocaine on infiltrative cutaneous analgesia. Lidocaine, a known local anesthetic, was used as control. ⋯ Intraperitoneal injection of co-administration of drugs (memantine or lidocaine) at ED95 with epinephrine (13.7nmol) produced no cutaneous analgesia (data not shown). Epinephrine, memantine, and lidocaine were shown to have local anesthetic effects as infiltrative cutaneous analgesia. Epinephrine increased the duration and potency of memantine and lidocaine as an infiltrative anesthetic.
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Neuroscience letters · Jun 2014
Somatostatin 4 receptor activation modulates TRPV1[correction of TPRV1] currents in dorsal root ganglion neurons.
Somatostatin (sst) is a cyclic neuropeptide known to have inhibitory roles in the central nervous system. It exerts its biological effects via the activation of the 5 sst receptor subtypes, which belong to the family of G-protein coupled receptors (GPCR). This peptide has analgesic properties, specifically via the activation of the sst4 receptor subtype. ⋯ The complete Freund's adjuvant (CFA) inflammatory pain model was used to examine if effects are augmented in pain conditions. The sst4 receptor agonist J-2156 was able significantly to inhibit capsaicin induced calcium and sodium influx, where the effect was more potent after CFA treatment. This inhibition identifies a contributory molecular mechanism to the analgesic properties of sst4 receptor activation.
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Neuroscience letters · Jun 2014
Fucoidan attenuates the existing allodynia and hyperalgesia in a rat model of neuropathic pain.
Fucoidan is an active constituent found in brown seaweeds, which have potential neuroprotection. The current study aimed to investigate the effects of fucoidan on the maintenance of neuropathic pain induced by L5 spinal nerve ligation (SNL) and the underlying mechanism related to the spinal neuroimmune responses. Animals were randomized into 5 groups: sham-operation with vehicle and SNL with vehicle or fucoidan (15, 50, and 100mg/kg). ⋯ The results showed that fucoidan caused dose-dependently attenuation of mechanical allodynia and thermal hyperalgesia. Furthermore, fucoidan could markedly inhibit neuroimmune activation characterized by glial activation, production of cytokines as well as ERK activation. The analgesic effect of intrathecal fucoidan in rats receiving SNL might partly attribute to the inhibition of neuroimmune activation associated with the maintenance of neuropathic pain.
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Small-fiber neuropathy was induced in young adult mice by intraperitoneal injection of resiniferatoxin (RTX), a TRPV1 agonist. At day 7, RTX induced significant thermal and mechanical hypoalgesia. At day 28, mechanical and thermal nociception were restored. ⋯ In summary, RTX induced in our model a transient neuropeptide depletion in sensory neurons without nerve degeneration. We think this model is valuable as it brings the opportunity to study functional nerve changes in the very early phase of small fiber neuropathy. Moreover, it may represent a useful tool to study the mechanisms of action of therapeutic strategies to prevent sensory neuropathy of various origins.
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Neuroscience letters · Jun 2014
Deficits of synaptic functions in hippocampal slices prepared from aged mice null α7 nicotinic acetylcholine receptors.
Alpha 7 (α7) nicotinic acetylcholine receptor (α7-nAChR) is one of most high expressed nAChR subtypes in the brain. The activation of nAChRs enhances animal cognitive, learning and memory abilities. However, the role of genetic knockout (KO) of α7-nAChRs in animal cognition-associated behaviors is still obscure. ⋯ However, adult α7-nAChR KO mice did not show a clear deficit in LTP although the basic synaptic transmission was also reduced compared to adult WT mice. In both age groups, there was no significant difference of paired-pulse facilitation between α7-nAChR KO and WT mice. Collectively, this study provides direct evidence, for the first time, that the impaired synaptic function occurs in aged α7-nAChR KO mice, suggesting an importance of α7-nAChRs in maintaining cognitive function during aging process.