Oxygen Consumption in the New‐born Rat and the Effects of Maternally Administered Analgesics

Absence of respiratory depression in the new-born rat after maternal administration of etorphine by the sublingual route

“…More recently the respiratory depressant effect of subcutaneous etorphine was shown again, this time in pregnant rats at term (Blane, 1967) although, surprisingly, the young delivered by Caesarian section from mothers that had received twice the ED80 for analgesia showed significantly less depression of oxygen consumption than did those from mothers receiving an equivalent dose of morphine or methadone. On the other hand, maternal doses of etorphine substantially above the analgesic ED80 resulted in some neonatal mortalityan effect which was seen to a lesser extent with methadone but which did not occur with morphine.…”

“…Maternal respiratory rates were measured before treatment and again 30 min later, before the mothers were killed by dislocation of the neck. The young were delivered immediately by Caesarian section and incubated individually in the chambers of a respirometer (Blane, 1967).…”