Maternal Separation Exhibits a Sex Dimorphism in Memory Impairments in Adolescent Rats: Acute Methylphenidate Administration as a Treatment

IntroductionRodents are highly dependent on maternal care after birth. Disturbing mother and pup interactions leads to detrimental alternations for the rat and the mother. Maternal separation (MS) is an accepted model for investigating disruption of mother and pup relationship. In addition to other detrimental effects, MS is a model known to induce permanent changes in learning and memory. Methylphenidate has been effective in memory enhancement in individuals suffering from memory deficits, attention-deficit hyperactive disorder (ADHD), as well as healthy subjects for better performance in exams.Material and MethodsIn this research, a 21-day separation for 3 h was implemented, and the effects of MS on spatial and passive avoidance learning, and memory were evaluated in the mid-adolescence period of rats, in both males and females. Also, a drug intervention of a high therapeutic dose of 5 mg per kg was used in a five-day period in different control and MS groups. Morris water maze was utilized for spatial learning and memory analysis, and a shuttle box paradigm was used for passive avoidance learning and memory.ResultsThrough our behavioral tests, we have shown that MS can alter spatial learning and memory in males. On the other hand, females are protected from the detrimental effects of MS on spatial learning and memory. Furthermore, passive avoidance learning was not different among groups, be it male or female. However, in the case of memory evaluation in the passive avoidance test, the male did not exhibit a significant difference in step-through latency. However, maternally separated females had poor performance in the memory phase with shorter step-through latencies.ConclusionMethylphenidate compensated for the deleterious effects of MS on learning and spatial memory for the male group and passive avoidance memory in the female group at the behavioral level.