Standardisation of evoked response, threshold reaction time and morphine doses for analgesia in newborn nourished and undernourished suckling rats to noxious stimulus.

ABSTRACT

In the present study, the different criterias to assess the analgesic response of morphine in newborn suckling rats on "Eddy's hot plate" were modified. Initially, the intensity of applied heat stimulus to evoke the "cut off response" was adjusted to 50 degrees C. Different reproducible characteristic cut off responses (running and turning on back or raising fore and hind paws alternately) were selected for newborn suckling rats of varying age groups. The results revealed that newborn suckling rats are highly sensitive to morphine. The doses of morphine needed for producing a reasonable degree of analgesia on body weight basis were 0.1 mg/kg for 9 days old rats and 1.0 mg/kg for 18 days old rats. This procedure seems to be of great value in studying the analgesic effect of a drug in newborn suckling rats.