Eating a high fat or ketogenic diet increases sensitivity of rats to methamphetamine-induced locomotion.

Eating a high fat diet leads to negative health consequences such as obesity and type 2 diabetes. Recent evidence also suggests that eating a high fat diet can impact drug sensitivity. For example, eating a high fat laboratory chow enhances the sensitivity of rats to the behavioral effects of drugs of abuse, including methamphetamine. Previous research has focused on diets that are high in fat and carbohydrates but low in protein. In contrast, a ketogenic diet is high in fat, low in carbohydrates, and low in protein. Ketogenic diets have been used in humans for the treatment of epilepsy and have been investigated for weight loss. Preclinical studies suggest that rats eating a ketogenic diet are less sensitive to the locomotor stimulating effects of cocaine (e.g., stereotypy). It was hypothesized that eating high fat chow would enhance sensitivity of rats to methamphetamine-induced locomotion and sensitization; however, rats eating ketogenic chow would not differ from rats eating standard chow. To test this hypothesis, rats eating standard chow (17% kcal from fat, 58% kcal from carbohydrate, 25% kcal from protein), high fat chow (60% kcal from fat, 21% kcal from carbohydrate, 18% kcal from protein), or ketogenic chow (90.5% kcal from fat, 0.3% kcal from carbohydrate, 9.2% kcal from protein) were tested once weekly with cumulative doses of methamphetamine (0.1-3.2 mg/kg; i.p.). After 4 weeks, rats eating high fat chow were more sensitive to the locomotor-stimulating effects of smaller and intermediate doses of methamphetamine (e.g., 0.32, 1.0 mg/kg) than rats eating standard chow. Rats eating ketogenic chow were also more sensitive than rats eating standard chow to the locomotor-stimulating effects of methamphetamine, but only at the largest dose tested (3.2 mg/kg). Future research will investigate the mechanisms underlying these diet-induced changes in methamphetamine sensitivity.