Activation of D1-like dopamine receptors is involved in the impairment of spatial memory in the offspring of morphine-abstinent rats

Abstract

Accumulating evidence suggests that epigenetic mechanisms play an essential role in the formation and maintenance of memory as well as addiction. In this study, we examined the role of D1-like dopamine receptor (D1 DR) on spatial memory in the offspring of morphine-abstinent rats. Adult male and female rats received morphine orally for 21 days and were drug-free for ten days. The rats were prepared to mate and the offspring were divided into four groups: offspring of drug-naïve parents, offspring of maternal morphine-exposed, offspring of paternal morphine-exposed, and PME + MME group. Saline or SCH23390 was injected into the hippocampus and prefrontal (PFC), and the Morris Water Maze task was performed. Afterward, the rats were sacrificed, and phosphorylated-CREB (p-CREB) was assessed using Western blotting. The data obtained from saline-treated offspring indicated that spatial memory was deteriorated in the offspring of morphine-abstinent parents compared with the control which improved when they received SCH23390. The level of p-CREB also decreased in the hippocampus, while it increased in the PFC and hippocampus after SCH23390 administration. Our results suggested that morphine exposure before conception could induce impairment in spatial memory in the offspring. Since D1 DR was up-regulated in the PFC of the offspring, blocking D1 DR led to improved memory deficit in the offspring of morphine-abstinent rats. Improvement of memory is correlated to p-CREB level in the hippocampus and PFC.