The effect of naloxone and morphine on convulsions in mice following withdrawal from nitrous oxide.

The incidence of withdrawal convulsions was determined in mice following removal from a 70 per cent nitrous oxide environment. Groups of 20 mice received saline (control), naloxone or morphine subcutaneous injections five minutes prior to withdrawal. The observer was blind to the treatments. In comparison to the control group, the proportion convulsing was significantly (p less than 0.05) increased following naloxone 0.125 mg (n = 40), 0.25 mg, but not 0.5 mg. The proportion convulsing was significantly decreased following morphine 0.4 mg. Overall proportions of mice convulsing was 0.55 for the saline control group; 0.73 for naloxone 0.125 mg; 0.80 for naloxone 0.25 mg; 0.60 for naloxone 0.50 mg; and 0.38 for morphine 0.4 mg. Modification of this phenomenon by both an opiate antagonist and agonist suggests endorphin withdrawal as a possible mechanism. However, this should be regarded as indirect evidence pending further study of this area.