Effect of opioid peptide antisera on nitrous oxide antinociception in rats

This study was performed to examine the effects of ICV injection of antiserum against beta-endorphin (beta-EP) or methionine-enkephalin (ME) on nitrous oxide-induced antinociception in rats using the hot plate test. The injection of beta-EP antiserum reversed the antinociceptive effect of nitrous oxide in a dose-related manner up to 200 micrograms/rat. However, antagonism of nitrous oxide by 400 micrograms beta-EP antiserum was comparable to that produced by 200 micrograms. On the other hand, similar amounts of ME antiserum had little effect against nitrous oxide antinociception. These findings suggest that beta-EP may play an important role in the antinociceptive effect of nitrous oxide.