Mol Pain
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Morphine consumption can vary widely between individuals even for identical surgical procedures. As mu-opioid receptor (OPRM1) is known to modulate pain perception and mediate the analgesic effects of opioid compounds in the central nervous system, we examined the influence of two OPRM polymorphisms on acute post-operative pain and morphine usage in women undergoing elective caesarean delivery. ⋯ Our results suggest that ethnicity and OPRM 118A>G genotype are independent and significant contributors to variation in pain perception and postoperative morphine use in patients undergoing cesarean delivery.
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Functional imaging has revolutionized the neurosciences. In the pain field it has dramatically altered our understanding of how the brain undergoes significant functional, anatomical and chemical changes in patients with chronic pain. However, most studies have been performed in adults. ⋯ Measures of changes in the brains of children have important implications in understanding neural plasticity in response to acute and chronic pain in the developing brain. Such findings may have implications for treatments in children affected by chronic pain and provide novel insights into chronic pain syndromes in adults. In this review we summarize this potential and discuss specific concerns related to the imaging of pain in children.
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Long-term potentiation (LTP), a much studied cellular model of synaptic plasticity, has not been demonstrated at synapses between primary afferent C-fibers and spinal dorsal horn (DH) neurons in mice in vivo. EphrinB-EphB receptor signaling plays important roles in synaptic connection and plasticity in the nervous system, but its role in spinal synaptic plasticity remains unclear. ⋯ This study provides an in vivo mouse model of LTP at synapses of C-fibers onto the superficial DH neurons that will be valuable for studying the DH neuron excitability and their synaptic plasticity and hyperalgesia. It further takes advantage of examining functional implications of a specific gene targeted mice and demonstrates that the EphB1 receptor is essential for development of LTP.
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The mammalian target of rapamycin (mTOR) is a key regulator of mRNA translation whose action can be inhibited by the drug rapamycin. Forms of long-term plasticity require protein synthesis and evidence indicates that mRNA in dendrites, axon terminals and cell bodies is essential for long-term synaptic plasticity. Specific to pain, shifts in pain thresholds and responsiveness are an expression of neuronal plasticity and this likely contributes to persistent pain. We investigated this by inhibiting the activity of mTOR with rapamycin at the spinal level, of rats that were subjected to the formalin test, using both behavioural and electrophysiological techniques. ⋯ We conclude that mTOR has a role in maintaining persistent pain states via mRNA translation and thus protein synthesis. We hypothesise that mTOR may be activated by excitatory neurotransmitter release acting on sensory afferent terminals as well as dorsal horn spinal neurones, which may be further amplified by descending facilitatory systems originating from higher centres in the brain.