Investigation of the Effect of Opioids on Experimental Hyperalgesia in Oesophagus and Skin, and in an Ischemic Model of Musclepain. Including an Explorative Study of the Effect of Morphine on the Pain Processing in the Brain

The study is a multi-modal multi-tissue human experimental pain study in 24 healthy volunteers. The study is a randomized cross-over study. The effect of 2 opioids, Oxycodone and Morphine will be compared on pain stimuli in skin, muscle an oesophagus. Hyperalgesia will be induced in skin by capsaicin and in oesophagus by a mixture of capsaicin and acid, to sensitize these tissues. The pain thresholds before and after opioid administration will be compared. The hypothesis is that the difference in effect of the opioids is more pronounced in the presence of hyperalgesia. As hyperalgesia is a common phenomenon the clinic, the findings in this study may lead to a better understanding of the treatment of pain. The study will include an explorative study of the effect of Morphine of pain processing in the brain, this will provide us with new insight in the effect of the opioids of pain processing in the brain.