Oxytocin protects against 3-NP induced learning and memory impairment in rats: Sex differences in behavioral and molecular responses to the context of prenatal stress.

Learning and memory impairment manifests years before the onset of motor impairments in Huntington's disease (HD). Oxytocin (OXT), as a neurohypophyseal neuropeptide has a key role in both learning and memory. Hence, we investigated possible protective effect of OXT on instrumental fear conditioning memory impairment by 3-Nitropropionic acid (3-NP) induced HD, considering sex and prenatal stress effects. Pregnant Wistar rats were exposed to restraint stress for 45 min three times a day, from the gestational day 8 to parturition. 3-NP was injected intraperitoneally (20 mg/kg) for 5-7 days after OXT (10 μg/μl. icv) injection in the male and female offspring rats respectively. One day after the last 3-NP injection, the rotarod and passive avoidance task were conducted. As the key molecular determinants in metabolism and memory processes, we measured the activity of acetylcholinesterase (AChE) and the amount of receptor interacting protein3 (RIP3) in the hippocampus, prefrontal cortex, striatum and amygdala using spectrophotometry and western blotting respectively. Besides, the activity of glutamate dehydrogenase was measured (GDH) as a chain between metabolism and memory formation. The results indicated that OXT improved learning and memory impairment caused by 3-NP or prenatal stress in both sexes. It was along with a significant decrease in the level of RIP3, AChE and GDH activities. However, in the presence of prenatal stress, the OXT could improve 3-NP induced learning and memory impairments just in female rats. So it could be suggested as an effective neurotherapeutic agent in diseases such as HD, but its sex and context dependency should be considered carefully.