Pain
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Multicenter Study Comparative Study
Social context and acceptance of chronic pain: the role of solicitous and punishing responses.
Much of the behavior of chronic pain sufferers happens in social contexts where social influences can play a role in their suffering and disability. Researchers have investigated relations of social responses with verbal and overt pain behavior and, more recently, with patient thinking, such as catastrophizing. There has not yet been a study of social influences on patient acceptance of chronic pain. ⋯ Primary results showed that, as predicted, both solicitous and punishing responses from significant others were negatively associated with acceptance of pain. These relations remained, independent of patient age, education, pain level, and level of general support from the significant other. These results suggest that social influences can play a role in patients' engagement in activity with pain present and their willingness to have pain without trying to avoid or control it.
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Comparative Study
Acute and persistent pain modulation of attention-related anterior cingulate fMRI activations.
The anterior cingulate cortex (ACC) has been implicated in both sustained attention (SA) and pain perception. Nonetheless, only a small body of literature has examined the relationship between SA and pain perception. This study utilized fMRI to examine activation patterns that emerged in the ACC in healthy participants and participants with chronic pain (due to osteoarthritis (OA) of the knee) while completing a sustained attention task with and without exposure to an acute painful stimulus. ⋯ In the healthy group, there were broadly distributed clusters of voxels within the ACC that were modulated by painful stimulation. But in the chronic pain group, a discrete focal region of the ACC was modulated by pain. These results demonstrate that ACC activity is modulated differently during tasks of SA and pain, and that acute pain in healthy participants and participants with chronic pain result in significantly different ACC activation patterns.
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Comparative Study
Differential susceptibility of the PAG and RVM to tolerance to the antinociceptive effect of morphine in the rat.
The periaqueductal gray (PAG) and rostral ventromedial medulla (RVM) are part of a nociceptive modulatory system. Microinjection of morphine into either structure produces antinociception. Tolerance develops to ventrolateral PAG mediated antinociception with repeated microinjection of morphine. ⋯ There was a 64% drop in hot plate latency from the first to the fifth injection of morphine into the PAG, but only a 36% drop in latency following RVM microinjections. Reducing the interdose interval to two injections a day or increasing the total number of injections from 4 to 8 did not enhance the development of tolerance to RVM morphine administration. These data demonstrate that opioid-sensitive neurons in the RVM are relatively resistant to the development of tolerance compared to PAG neurons.
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Comparative Study
Enhanced excitability of dissociated primary sensory neurons after chronic compression of the dorsal root ganglion in the rat.
A chronic compression of the dorsal root ganglion (CCD) produces ipsilateral cutaneous hyperalgesia and allodynia in rats. Intracellular electrophysiological recordings from formerly compressed neurons in the intact dorsal root ganglion (DRG) reveal lower than normal current thresholds (CTs) and abnormal spontaneous activity (SA) (Zhang JM, Song XJ, LaMotte RH. Enhanced excitability of sensory neurons in rats with cutaneous hyperalgesia produced by chronic compression of the dorsal root ganglion. ⋯ The overall incidence of SA was higher for CCD than for control neurons after 1d culture (10.3 vs. 1.8%) and similar to that obtained in the intact DRG. We conclude that the CCD-induced hyperexcitability of medium- and large-sized neurons remains after dissociation and is intrinsic to the soma. For small-sized neurons, the effects of CCD observed in the intact DRG are less apparent after dissociation possibly due to the hyperexcitability produced by the dissociation process itself.