Pain
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Dental pain, including toothache, is one of the most prevalent types of orofacial pain, causing severe, persistent pain that has a significant negative effect on quality of life, including eating disturbances, mood changes, and sleep disruption. As the primary cause of toothache pain is injury to the uniquely innervated dental pulp, rodent models of this injury provide the opportunity to study neurobiological mechanisms of tissue injury-induced persistent pain. Here we evaluated behavioral changes in mice with a dental pulp injury (DPI) produced by mechanically exposing the pulp to the oral environment. ⋯ Surprisingly, mice with DPI increased their consumption of sucrose solution, to over 150% of baseline, regardless of temperature. Both the weight loss and increased sucrose intake in the first 2 days of injury were reversed by administration of indomethacin. These findings indicate that enhanced sucrose consumption may be a reliable measure of orofacial pain in rodents, and suggest that alterations in energy expenditure and motivational behaviors are under-recognized outcomes of tooth injury.
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Voltage-gated Na(+) channels (Nav) are the targets of a variety of scorpion toxins. Here, we investigated the effects of Amm VIII, a toxin isolated from the venom of the scorpion Androctonus mauretanicus mauretanicus, on pain-related behaviours in mice. The effects of Amm VIII were compared with the classic scorpion α-toxin AaH II from Androctonus australis. ⋯ AaH II and Amm VIII reduced first spike latency and lowered action potential threshold. Amm VIII was less efficient than AaH II in increasing the gain of the firing frequency-stimulation relationship. In conclusion, our data show that Amm VIII, although less potent than AaH II, acts as a gating-modifier peptide reminiscent of classic α-toxins, and suggest that its hyperalgesic effects can be ascribed to gain-of-function of TTX-S Na(+) channels in nociceptors.
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Conditioned pain modulation (CPM) (ie, diffuse noxious inhibitory controls) is characterized by reduced perception of pain caused by intense pain in a remote body area. The conditioning stimuli used to trigger CPM causes pain, but also important cardiovascular responses. Higher blood pressure has been associated with reduced pain sensitivity. ⋯ A significant positive association was observed between CPM magnitude and the increase in blood pressure during the CPT. These results show that resting blood pressure values are related to acute pain tolerance, while descending pain inhibition is associated with increases in blood pressure. The rise in blood pressure caused by the conditioning stimulus is an important factor predicting the extent of endogenous pain inhibition in healthy subjects.
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We tested whether the combination of a reduced dose of a local anesthetic (LA) with an opioid compared with a standard dose of the same LA alone guaranteed adequate intraoperative anesthesia and postoperative analgesia and decreased LA-related adverse effects. We systematically searched (to November 2012) for randomized comparisons of combinations of a reduced dose of an LA with a concomitant opioid (experimental) with a standard dose of the LA alone (control) in adults undergoing surgery with single-injection intrathecal anesthesia without general anesthesia. We included 28 trials (1393 patients). ⋯ There was also evidence of a decrease in the risk of shivering (risk ratio [RR]: 0.26; 95% confidence interval [CI]: 0.12-0.56), nausea (RR: 0.45; 95% CI: 0.31-0.66), and arterial hypotension (RR: 0.52; 95% CI: 0.35-0.78). The risk of pruritus was increased (RR: 11.7; 95% CI: 6.2-21.9). Adding an opioid to a reduced dose of an intrathecal LA can decrease LA-related adverse effects and improve recovery from the spinal block without compromising intraoperative anesthesia or duration of postoperative analgesia.