Voluntary exercise does not ameliorate spatial learning and memory deficits induced by chronic administration of nandrolone decanoate in rats

Abstract

Chronic exposure to the anabolic androgenic steroids (AAS) nandrolone decanoate (ND) in supra-physiological doses is associated with learning and memory impairments. Given the well-known beneficial effects of voluntary exercise on cognitive functions, we examined whether voluntary exercise would improve the cognitive deficits induced by chronic administration of ND. We also investigated the effects of ND and voluntary exercise on hippocampal BDNF levels. The rats were randomly distributed into 4 experimental groups: the vehicle-sedentary group, the ND-sedentary group, the vehicle-exercise group, and the ND-exercise group. The vehicle-exercise and the ND-exercise groups were allowed to freely exercise in a running wheel for 15days. The vehicle-sedentary and the ND-sedentary groups were kept sedentary for the same period. Vehicle or ND injections were started 14days prior to the voluntary exercise and continued throughout the 15days of voluntary exercise. After the 15-day period, the rats were trained and tested on a water maze spatial task using four trials per day for 5 consecutive days followed by a probe trial two days later. Exercise significantly improved performance during both the training and retention of the water maze task, and enhanced hippocampal BDNF. ND impaired spatial learning and memory, and this effect was not rescued by exercise. ND also potentiated the exercise-induced increase in hippocampal BDNF levels. These results seem to indicate that voluntary exercise is unable to improve the disruption of cognitive functions by chronic ND. Moreover, increased levels of BDNF may play a role in ND-induced impairments in learning and memory. The harmful effects of ND and other AAS on learning and memory should be taken into account when athletes decide to use AAS for performance or body image improvement.