2-Mercaptoacetate does not stimulate chow intake in periweanling rats

In adult rats, administration of drugs that suppress oxidation of fatty acids, like mercaptoacetate (MA), produces increases in food intake. During development, the consequences of administration of MA are more varied. For example, in very young pups, intake of milk diets is unaffected by MA, while pups aged 12 to 15 days demonstrate increases in intake. However, in 18- and 21-day-old rats, milk intake is suppressed by administration of MA. Typically, the paradigms used to test rat pups differ significantly from those used to assess intake in adult rats. The present experiments were designed to examine whether 18-day-old pups tested with adultlike paradigms showed adultlike responses to administration of MA. In the first experiment, rat pups aged 18 days were injected with 0 or 68.4 mg/kg MA, then given 60-min tests while consuming either milk or chow diets that were novel, or to which they had previously been exposed. The results demonstrated that chow intake was not affected by administration of MA, but milk intake in experienced animals was suppressed by MA. Experiment 2 demonstrated that in contrast to administration of MA, 18-day-old pups deprived of food overnight showed increases in intake of chow and milk diets. In Experiment 3, when the effects of a range of doses of MA (22.8, 45.6, 68.4 and 91.2) on chow intake over a 4-h period were assessed, all doses of MA produced a significant suppression of chow intake in 18-day-old pups. Taken together, the data suggest that alterations in fatty acid oxidation produced by administration of MA do not stimulate chow intake in periweanling pups tested in an adultlike fashion.