Journal of pharmacological sciences
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Tramadol is an analgesic that is used worldwide, but its mechanisms of action have not been elucidated. It has been speculated that tramadol acts primarily through the activation of micro-opioid receptors and the inhibition of monoamine reuptake. The majority of studies to date have focused on ion channels in the central nervous system as targets of anesthetics and analgesics. ⋯ Several studies have shown that GPCRs and ion channels are targets for analgesics and anesthetics. In particular, tramadol has been shown to affect GPCRs, including muscarinic acetylcholine receptors and 5-hydroxytryptamine receptors. Here, the effects of tramadol on monoamine transporters, GPCRs, and ion channels are presented, and recent research on the pharmacology of tramadol is discussed.
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Ginseng, the root of Panax species, is a well-known herbal medicine. It has been used as a traditional medicine in China, Korea, and Japan for thousands of years and is now a popular and worldwide used natural medicine. The active ingredients of ginseng are ginsenosides which are also called ginseng saponins. ⋯ In general, antioxidant, anti-inflammatory, anti-apoptotic, and immune-stimulatory activities are mostly underlying the possible ginseng-mediated protective mechanisms. Next to animal studies, data from neural cell cultures contribute to the understanding of these mechanisms that involve decreasing nitric oxide (NO), scavenging of free radicals, and counteracting excitotoxicity. In this review, we focus on recently reported medicinal effects of ginseng and summarize the current knowledge of its effects on CNS disorders and neurodegenerative diseases.
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Gabapentin, a gamma-aminobutyric acid (GABA) analogue anticonvulsant, is also an effective analgesic agent in neuropathic and inflammatory, but not acute, pain systemically and intrathecally. Other clinical indications such as anxiety, bipolar disorder, and hot flashes have also been proposed. ⋯ Different mechanisms might be involved in different therapeutic actions of gabapentin. In this review, we summarized the recent progress in the findings proposed for the antinociceptive action mechanisms of gabapentin and suggest that the alpha(2)delta subunit of spinal N-type Ca(2+) channels is very likely the analgesic action target of gabapentin.
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We have been studying the role of ATP receptors in pain and already reported that activation of P2X(2/3) heteromeric channel/receptor in primary sensory neurons causes acutely tactile allodynia, one hallmark of neuropathic pain. We report here that tactile allodynia under the chronic pain state requires an activation of the P2X(4) ionotropic ATP receptor and p38 mitogen-activated protein kinase (MAPK) in spinal cord microglia. Two weeks after L5 spinal nerve injury, rats displayed a marked mechanical allodynia. ⋯ Moreover, intraspinal administration of a p38MAPK inhibitor, SB203580, suppressed the allodynia. We also found that the expression level of P2X(4) was increased strikingly in spinal cord microgila after nerve injury and that pharmacological blockade or inhibition of the expression of P2X(4) reversed the allodynia. Taken together, our results demonstrate that activation of P2X(4) or p38MAPK in spinal cord microglia is necessary for tactile allodynia after nerve injury.