The present study investigated metaplasticity-related mRNA expressions in valproic acid (VPA)-rats, focusing on the PI3K/AKT pathway. Wistar dams were treated with a single intraperitoneal injection of 600 mg/kg VPA or saline on embryonic day E12.5 or an equal volume of saline solution. Three behavioral tests were conducted on these males' offspring: grid-walking test, negative geotaxis test, and three-chamber social interaction test. Metaplasticity was induced in 60-day-old male progeny by giving high-frequency stimulation for 5 minutes following low-frequency stimulation to the perforant pathway. For the baseline stimulation protocol (n = 6), stimulation was delivered to the dentate gyrus at the previously determined stimulation intensity (0.33 Hz 0.175 msec 30 s) for 75 min. The percent change of slope of field excitatory postsynaptic potential (fEPSP) and amplitude of population spike were calculated 55-60 min after induction protocol. The mRNA levels of PI3K, PTEN, AKT, GSK-3β, and MAPT were measured in the hippocampus by using quantitative rt-PCR. We found that offspring of VPA-treated rats showed significantly impaired sensorimotor coordination, decreased sociability, impaired preference for social novelty, and reduced input-output curve of fEPSP slope, compared to control animals. Despite a similar metaplastic response, mRNA levels of genes of interest were similar but considerably down-regulated after induction in offspring of VPA-treated dams. Our study provides evidence that the induced expression of autism-related genes has evolved to enable an adaptation mechanism during metaplastic control of long-term potentiation.
Keywords: autism; dentate gyrus; metaplasticity; valproic acid.
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