Continuous naloxone administration via osmotic minipump decreases autotomy but has no effect on nociceptive threshold in the rat.

Rats with unilaterally sectioned sciatic nerves were continuously administered naloxone HCl (80 or 800 micrograms/h) or equivalent volumes of saline (1 or 10 microliters/h) subcutaneously via osmotic minipumps over a 2 or 5 week period. Rats receiving 80 micrograms/h naloxone for 5 weeks exhibited significantly less self-mutilation (autotomy) of the denervated foot than saline controls or rats receiving 80 micrograms/h naloxone for 2 weeks. The nociceptive threshold of intact rats infused with the same dose of naloxone was tested on a hot plate.

Stress-related pain behavior in rats with peripheral nerve injuries.

The effects of cold stress were studied on rats with unilaterally sectioned sciatic nerves. Behaviors suggestive of pain occurred in a number of these animals. These behaviors vanished when removing the rats from the stressful environment.

The effect of dorsal column stimulation on the nociceptive response of dorsal horn cells and its relevance for pain suppression.

The effect of single and repetitive electrical stimulation of the dorsal columns on cells in laminae IV and V of the ipsilateral dorsal horn at S1 was examined in spinalized cats. About two-thirds of the cells responded to thermal nociceptive cutaneous stimulation and of these most responded also to low threshold mechanical stimulation. The other one-third of the cells were innervated by mechanoreceptors including type I or Haarscheiben.