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.

Nociceptors and warm receptors innervated by C fibres in human skin.

The properties of 125 C fibre units recorded from the peripheral nerves of conscious man were studied. On the basis of receptive field properties and responses to natural stimulation, 120 of the units were classified as polymodal C nociceptors. Five of the units were identified as specific C warm receptors.