dynorphins and Mycobacterium-Infections

Inoculation of rats with Mycobacterium butyricum produced an arthritis of the limbs which revealed an enhanced sensitivity to noxious mechanical pressure (hyperalgesia). Arthritic rats displayed a pronounced rise in immunoreactive dynorphin in lumbo-sacral spinal cord which correlated both with the intensity and time-course of this hyperalgesia. MR-2266, a relatively preferential antagonist at the chi-opioid receptor (at which dynorphin is considered to act) potentiated this hyperalgesia. In contrast, MR 2267 (its inactive stereo-isomer) was ineffective. Further, naloxone (a weak chi-antagonist), and ICI 154,129 (a preferential delta-antagonist) were, in each case, inactive. The data demonstrate a pronounced response of spinal dynorphin to chronic arthritic pain in the rat. In addition, they raise the possibility of a function of spinal DYN, via a chi-receptor, in the modulation of chronic arthritic pain.

Topics: Animals; Arthritis; Chronic Disease; Conditioning, Classical; Dynorphins; Enkephalin, Methionine; Mycobacterium Infections; Naloxone; Nociceptors; Pain; Radioimmunoassay; Rats; Receptors, Opioid; Receptors, Opioid, kappa; Spinal Cord