Swimming reduces the severity of physical and psychological dependence and voluntary morphine consumption in morphine dependent rats

Eur J Pharmacol. 2015 Jan 15;747:88-95. doi: 10.1016/j.ejphar.2014.11.042. Epub 2014 Dec 10.


Previous studies have indicated that voluntary exercise decreases the severity of the anxiogenic-like behaviors in both morphine-dependent and withdrawn rats. This study examined the effects of regular swimming exercise during the development of dependency and spontaneous morphine withdrawal on the anxiety-depression profile and voluntary morphine consumption in morphine dependent rats. The rats were chronically treated with bi-daily doses (10 mg/kg, at 12h intervals) of morphine over a period of 14 days. The exercising rats were allowed to swim (45 min/d, five days per a week, for 14 or 21 days) during the development of morphine dependence and withdrawal. Then, rats were tested for the severity of morphine dependence, the elevated plus-maze (EPM), sucrose preference test (SPT) and voluntary morphine consumption using a two-bottle choice paradigm in animal models of craving. The results showed that withdrawal signs were decreased in swimmer morphine dependent rats than sedentary rats (P<0.05). Also, the swimmer morphine-dependent and withdrawn rats exhibited an increase in EPM open arm time and entries (P<0.05), higher levels of sucrose preference (P<0.001) than sedentary rats. Voluntary consumption of oral morphine was less in the swimmer morphine-withdrawn rats than the sedentary groups during four periods of the intake of drug (P<0.01). We conclude that regular swimming exercise reduces the severity of morphine dependence and voluntary morphine consumption with reducing anxiety and depression in morphine-dependent and withdrawn rats. Thus, swimming exercise may be a potential method to ameliorate some of the deleterious behavioral consequences of morphine dependence.

Keywords: Anxiety; Craving; Depression; Morphine-dependent and withdrawn rats; Swimming exercise.

MeSH terms

  • Animals
  • Anxiety / complications
  • Anxiety / therapy
  • Craving
  • Depression / complications
  • Depression / therapy
  • Male
  • Morphine / pharmacology*
  • Morphine Dependence / complications
  • Morphine Dependence / psychology*
  • Morphine Dependence / therapy*
  • Physical Conditioning, Animal
  • Rats
  • Rats, Wistar
  • Substance Withdrawal Syndrome / complications
  • Substance Withdrawal Syndrome / psychology
  • Substance Withdrawal Syndrome / therapy
  • Swimming / psychology*


  • Morphine