Pain
-
The present study was undertaken to examine the involvement of descending pain modulatory systems from the brainstem rostral ventromedial medulla (RVM) in modulating visceral hyperalgesia produced by intracolonic instillation of zymosan. Three hours after intracolonic zymosan, the visceromotor response (VMR) to noxious colorectal distension (CRD, 80 mmHg, 20s) was increased significantly. This hyperalgesia was attenuated in a dose-dependent manner by the selective NMDA receptor antagonist APV (10-30 fmol, 1 microl) microinjected into the RVM. ⋯ In contrast to the effects of APV and L-NAME, administration of the non-NMDA receptor antagonist DNQX into the RVM further enhanced the already facilitated VMR to CRD in zymosan-treated rats. Taken together, these data suggest that zymosan-produced visceral hyperalgesia is influenced by two descending pain modulatory systems: a facilitatory system mediated by activation of NMDA receptors in the RVM and production of nitric oxide, and an inhibitory system mediated by activity at non-NMDA receptors in the RVM. The unmasking of one system by selective blockade of the other suggests simultaneous activation of both by colonic inflammation.
-
While attitudes toward pain have been identified as important mediators of patient adjustment to pain and response to treatment, research to date has focused on single attitude scales. The present study examined relations between attitude profiles and a set of variables reflecting clinical status in 395 chronic pain patients seen through a comprehensive pain center. A clustering procedure identified four distinct patient clusters, two of which displayed self-reliant attitude sets and two of which displayed medically oriented attitudes. ⋯ The medically oriented groups differed in terms of level of distress, with the more distressed group reporting pain of a greater duration. The results suggest that patients can be classified into attitudes profiles that are associated with meaningful differences in clinical status. Further research should investigate attitudes among more functional patients with chronic pain, especially as they affect the evolution of chronic pain syndromes.