Pain
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The nucleus of the solitary tract (NTS) contains pro-opiomelanocortin (POMC) neurons that are 1 of the 2 major sources of β-endorphin in the brain. The functional role of these NTS POMC neurons in nociceptive and cardiorespiratory function is debated. We have shown that NTS POMC optogenetic activation produces bradycardia and transient apnoea in a working heart-brainstem preparation and chemogenetic activation with an engineered ion channel (PSAM) produced opioidergic analgesia in vivo. ⋯ Inhibiting NTS POMC neurons does not produce any effect on basal nociception but inhibits stress-induced analgesia (unlike inhibition of arcuate POMC neurons). Activation of NTS POMC neuronal populations in conscious mice did not cause respiratory depression, anxiety, or locomotor deficit (in open field) or affective preference. These findings indicate that NTS POMC neurons play a key role in the generation of endorphinergic endogenous analgesia and can also regulate cardiorespiratory function.
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Randomized Controlled Trial
Referred sensation location can be altered by a strong heterotopic nociceptive stimulus: Implications for clinical pain conditions.
Referred sensations (RS) are a common clinical phenomenon in patients with musculoskeletal pain; however, the underlying mechanisms of RS and implications for diagnosis and management are poorly understood. The location of referral seems to have a preferred site, but studies have suggested it can be redirected to a site of previous injury and pain. However, it is not known if the same phenomenon can occur for a much shorter-lasting painful stimulus in the trigeminal system. ⋯ However, the RS location was displaced on average 1.2 cm between the baseline and postinfusion assessments for the hypertonic saline infusion, which was significantly increased when compared with the isotonic saline infusion which was on average 0.4 cm. These novel findings indicate the potential to modify the location of RS in the trigeminal system following a relatively brief noxious input. Clinicians need to be aware of the possible rerouting of RS in patients with complex orofacial pain.