The journal of pain : official journal of the American Pain Society
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Corneal injury can produce photophobia, an aversive sensitivity to light. Using topical application of lidocaine, a local anesthetic, and tetrodotoxin (TTX), a selective voltage-sensitive sodium channel blocker, we assessed whether enhanced aversiveness to light induced by corneal injury in rats was caused by enhanced activity in corneal afferents. Eye closure induced by 30 seconds of exposure to bright light (460-485 nm) was increased 24 hours after corneal injury induced by de-epithelialization. ⋯ Given the well-established corneal toxicity of local anesthetics, we suggest TTX as a therapeutic option to treat photophobia and possibly other symptoms that occur in clinical diseases that involve corneal nociceptor sensitization. Perspective: We show that lidocaine and TTX attenuate photophobia induced by corneal injury. Although corneal toxicity limits use of local anesthetics, TTX may be a safer therapeutic option to reduce the symptom of photophobia associated with corneal injury.
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Parental history of chronic pain has been associated with self-reported pain in adolescent offspring. This suggests that there may be neurobiological mechanisms associated with pain heritability. Because emotional circuitry is an important component of pain processing and may also influence cognition, we used functional magnetic resonance imaging to examine affective processing and cognitive control using an Emotional Go/NoGo task in youth with (FH + Pain, n = 8) and without (FH - Pain, n = 8) a parental history of chronic pain (mean age = 14.17 ± .34 years). ⋯ The current findings indicate differences in both emotional processing and cognitive control brain response in FH + Pain compared with FH - Pain youth, suggesting that both affective and executive functioning pathways may be important markers related to the intergenerational transmission of pain. Perspective: This is the first study to examine neurobiological markers of pain risk in adolescents with a family history of chronic pain. These findings may aid in the identification of neural phenotypes related to vulnerability for the onset of pain in at-risk youth.
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Several cross-sectional studies have reported a common comorbidity between depression and fibromyalgia syndrome (FMS). However, a bidirectional temporal association between these 2 distinct diseases has rarely been investigated. Using the Taiwan National Health Insurance Research Database, 25,969 patients with FMS and without any psychiatric disorder and 17,142 patients with depression and without FMS between 2000 and 2008 were enrolled and separately compared with age- and sex-matched (1:4) control groups. ⋯ Further study may be necessary to determine the underlying mechanism between depression and FMS and to clarify whether a prompt intervention for depression or FMS may decrease the risk of the other later in life. Perspective: Our study supported a bidirectional temporal association between depression and FMS such that each disease occurring first may increase the risk of the other subsequently. This result may imply a shared pathophysiology between FMS and depression, but further investigation is needed.
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Depression may be a critical factor in the initiation and maintenance of opioids. This study investigated the association among opioid use, pain, and depression in patients evaluated at a university-based outpatient pain clinic. Of the 2,104 new patients included, 55.89% reported current opioid use and showed a worse phenotypic profile (eg, higher pain severity, worse physical functioning) compared with nonopioid users. ⋯ Perspective: This study investigated the association among opioid use, pain, and depression at a university-based outpatient pain clinic. Depression emerged as a moderator of the relationship among opioid use, pain severity, and physical functioning. These findings lend support to the hypothesis that patients may be self-medicating affective pain with opioids.