The Form of Magnesium Fed Early in Life Has Subtle Effects on Open Field Behavior and Acoustic Startle Response, but Does Not Impact Morris Water Maze Performance

Abstract

Magnesium is an essential mineral that serves as an intracellular cofactor in enzymatic reactions and has an important regulatory role of gating of the N‐methyl‐D‐aspartate receptor (which is involved in learning and memory processing). The purpose of this study was to assess the impact of Magnesium Oxide (MgO) versus Magnesium L‐Threonate (MgT) during normal early postnatal development on anxiety‐related behaviors and cognition in rodents. Newly weaned Sprague‐Dawley rats, postnatal day (PD) 21, were fed a diet that either contained 0.1% MgO or 0.1% MgT. No significant differences were found for body weights or food intake across the study. Open field exploration of PD28 or PD35 rats resulted in a main effect of age (F=2.14, p<0.05) and an age by diet interaction (F=2.45 p<0.05). Rats fed MgO spent less time positioned near the wall at P28 (M 452.5s) than P35 (M 467.5 s) while MgT fed rats spent more time near the apparatus wall at P28 (M 482s) than P35 (M 355s). Percent change in startle response in acoustic startle chamber showed no significant differences between MgO and MgT on PD 28 whereas after two weeks of diet exposure MgT females sensitized to the startle stimulus. In Morris water maze testing, there was a main effect of time (F=22.275 p<0.001) during the training phase on latency to find the hidden platform, but no effect of diet. There was also no effect of diet on latency or % time in target quadrant during the probe trial. Overall, these data suggest the form of dietary magnesium provided early in life caused a subtle shift in development of exploratory behavior and associative learning but did not alter spatial learning or memory.Support or Funding InformationStudy funded by Mead Johnson Nutrition.