Effects of Regular Swimming Exercises on Severity of Naloxone- Precipitated Morphine Withdrawal Signs in Rats

Development of effective ways to impede drug-induced synaptic changes can play a vital role in the treatment and prevention of relapse as a clinical problem. Previous studies suggest that exercise decreases the sensitivity to the rewarding effects of morphine in rats. This study was designed to investigate the effects of regular swimming exercises on naloxone-precipitated morphine withdrawal signs in rats. In this study، 16 rats were divided into the control and experimental groups. The rats were injected with bi-daily doses (10 mg/kg، at 12 hr intervals) of morphine over a period of 14 days during swimming exercises. Exercised rats were submitted to swimming sessions (45 min/d، five days per a week، for 14 days). On day 15، after an acute injection of naloxone (2 mg/kg، IP) 2 h after receiving morphine injection according to a modified version of the Gellert–Holtzman scale، morphine dependent intensity was measured in both groups (swimmer and none swimmer). The results showed that withdrawal signs including abdominal contractions (P= 0. 000)، wet dog shakes (P= 0. 005)، weight loss (24h) (P= 0. 001)، jumps (P= 0. 002) and overall Gellert–Holtzman score (P= 0. 000) were significantly lower in the swimmer morphine treated rats as compared with non-swimmer control ones (P= 0. 0001). Among the evaluated signs، the number of rats per group with erection and genital grooming (62. 5%، P=0. 05)، diarrhea (40%، P=0. 025) and writhing (50%، P=0. 025) displayed a decrease in swimmer morphine treated rats compared to non-swimmer rats. Our findings indicate that regular swimming exercises can minimize severity of dependency upon morphine in rats.