Effects of voluntary exercise on anxiety-like behavior and voluntary morphine consumption in rat pups borne from morphine-dependent mothers during pregnancy

Exposure to morphine during pregnancy produced long-term effects in offspring behaviors. Recent studies have shown that voluntary exercise decreases the severity of anxiety behaviors in both morphine-dependent and withdrawn rats. Thus, the aims of the present study were to examine whether maternal exercise decreases prenatal dependence-induced anxiety and also, voluntary consumption of morphine in animal models of craving in rat pups. Pregnant rats were made dependent by chronic administration of morphine in drinking water simultaneously with access to a running wheel that lasted at least 21 days. Then, anxiety-like behaviors using the elevated plus-maze (EPM) and voluntary consumption of morphine using a two-bottle choice paradigm (TBC) were tested in male rat pups. The results showed that the rat pups borne from exercising morphine-dependent mothers exhibited an increase in EPM open arm time (P < 0.0001) and entries (P < 0.05) as compared with the sedentary groups. In animal models of craving showed that voluntary consumption of morphine in the rat pups borne from exercising morphine-dependent mothers was less in the second (P < 0.032) and third (P < 0.014) periods of intake as compared with the sedentary group. This study showed that maternal exercise decreases the severity of the anxiogenic-like behaviors and voluntary consumption of morphine in rat pups.