The effects of magnesium deficiency of ketamine sleeping times in the rat.

Young growing rats were maintained on a magnesium deficient diet, and injected with ketamine after 7, 11, 14, and 18 days on the diet. A comparison of the sleeping times, as measured by the loss of the righting reflex after injections of three doses of ketamine, was made with rats similarly maintained on a control diet. Tolerance with successive injections to ketamine, indicated by a decrease in sleeping time, was noted only among the control rats. After 14 and 18 days on the diet, the magnesium deficient rats showed no tolerance to the earlier injections, but their sleeping times were longer than their control counterparts. In rats injected for the first time on day 14 of the diet, the magnesium deficient rats showed significantly longer sleeping times than the control rats; this suggests that the difference in sleeping times between groups is not entirely dependent upon the development of tolerance to the drug seen in the control rats. In addition, a sex difference was noted, with female rats sleeping longer with ketamine than male rats.