Swimming exercise during morphine abstinence in parents-to-be attenuated morphine-induced conditioned place preference and locomotor sensitization only in male rat offspring

•Male offspring of the morphine-abstinent parents-to-be exhibited a morphine CPP.•Swimming in morphine-abstinent parents-to-be attenuated morphine reward in male offspring.•Swimming in morphine-abstinent parents-to-be attenuated locomotor sensitization in male offspring. This study was designed to examine the effects of swimming exercise during morphine abstinence in parents-to-be before mating on morphine-induced conditioned place preference (CPP) and locomotor sensitization in the pubertal male and female rat offspring. Male and female Wistar rats were injected with bi-daily doses (10 mg/kg, 12 h intervals) of morphine for 14 days. The exercising rats exposed to a regular swimming exercise (45 min/d, five days per a week) during 30 days of morphine abstinence before mating. Then, the pubertal male and female rat offspring were tested for morphine-induced CPP and locomotor sensitization (using the open field). The results showed that the pubertal male offspring of the morphine-abstinent parents-to-be exhibited an increase in CPP to morphine and locomotor activity after morphine challenge than the offspring from the control group. While, swimming exercise in morphine-abstinent parents-to-be decreased CPP score and locomotor activity in the pubertal male offspring than control offspring. Thus, exposure to swimming exercise in morphine-abstinent parents-to-be before mating may exert a protective effect against morphine-induced reward and locomotor sensitization in their pubertal offspring which may prevent the vulnerability of the first generation to drug abuse following opiate-addicted parents before mating.