Pain
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Glutamate serves as the primary excitatory neurotransmitter in the nervous system. Previous studies have identified a role for glutamate and group I metabotropic receptors as targets for study in peripheral inflammatory pain. However, the coordination of signaling events that transpire from receptor activation to afferent neuronal sensitization has not been explored. ⋯ In dissociated primary afferent neurons, mGluR5 activation increases TRPV1 responses in an AKAP-dependent manner through a mechanism that induces AKAP association with TRPV1. Experimental results presented herein identify a mechanism of receptor-driven scaffolding association with ion channel targets. Importantly, this mechanism could prove significant in the search for therapeutic targets that repress episodes of acute pain from becoming chronic in nature.
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Elevated nerve growth factor (NGF) in the contralateral dorsal root ganglion (DRG) mediates mirror-image pain after peripheral nerve injury, but the underlying mechanism remains unclear. Using intrathecal injection of NGF antibodies, we found that NGF is required for the development of intra-DRG synapse-like structures made by neurite sprouts of calcitonin gene-related peptide (CGRP(+)) nociceptors and sympathetic axons onto neurite sprouts of Kv4.3(+) nociceptors. ⋯ Furthermore, neutralizing the neurotransmitter norepinephrine or CGRP in the synapse-like structures by antibodies has similar analgesic effect. Thus, elevated NGF after peripheral nerve injury induces neurite sprouting and the formation of synapse-like structures within the contralateral DRG, leading to the development of chronic mirror-image pain.
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Review Meta Analysis
Offspring of Parents with Chronic Pain: A Systematic Review and Meta-Analysis of Pain, Health, Psychological, and Family Outcomes.
Offspring of parents with chronic pain may be at risk for poorer outcomes than offspring of healthy parents. The objective of this research was to provide a comprehensive mixed-methods systematic synthesis of all available research on outcomes in offspring of parents with chronic pain. A systematic search was conducted for published articles in English examining pain, health, psychological, or family outcomes in offspring of parents with chronic pain. ⋯ No significant differences were found on teacher-reported externalizing problems. The meta-ethnography identified 6 key concepts (developing independence, developing compassion, learning about health and coping, missing out, emotional health, and struggles communicating with parents). Across study designs, offspring of parents with chronic pain had poorer outcomes than other offspring, although the meta-ethnography noted some constructive impact of having a parent with chronic pain.
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Randomized Controlled Trial
Effects of a T-type calcium channel blocker, ABT-639, on spontaneous activity in C-nociceptors in patients with painful diabetic neuropathy: a randomized controlled trial.
T-type calcium channels are a potential novel target for treatment of neuropathic pain such as painful diabetic neuropathy. ABT-639 is a peripherally acting highly selective T-type Ca(v)3.2 calcium channel blocker that has demonstrated analgesic efficacy in preclinical models and may have the potential to reduce spontaneous fiber activity. Microneurography is a unique technique that directly assesses the function of peripheral sensory afferents and measures abnormal spontaneous activity in single peripheral nociceptive C fibers. ⋯ Further research of T-type Ca(v)3.2 calcium channels as potential treatment targets for painful diabetic neuropathy is warranted. The utilization of microneurography as a means to measure abnormal activity in C-nociceptors in human clinical studies opens new possibilities for future studies of compounds targeting peripheral nerve hyperexcitability. ClinicalTrials.gov identifier: NCT01589432.