Poster Topical Area: Neurobiology

Location: Hall D

Poster Board Number: 714

P16-012 - Adiposity Mediates Effects of Monosodium Glutamate on Learning in Rats

Monday, Jun 11
8:00 AM – 3:00 PM

The objective of this research was to evaluate the effects of dietary monosodium glutamate (MSG) on brain function in rats. Twenty-two week-old male Sprague Dawley rats were trained to solve two concurrent learning and memory problems. One was a conditional discrimination problem (i.e., a serial feature negative task), in which a brief auditory cue signaled the delivery of sucrose pellets, except on trials where that cue was preceded by a visual stimulus). The ability to solve this problem depends on the functional integrity of the hippocampus. The other problem was a simple discrimination (i.e., one auditory cue signaled sucrose, another did not) that can be solved by rats without a hippocampus and appears to depend on brain circuitry in the striatum. After the rats solved both of these problems, they were subdivided into four groups with each group maintained ad libitum on one of four diets: standard low-fat high carbohydrate chow, chow + MSG, a western diet (WD) high in sugar and fat, or a western diet + MSG. The effects of these diets on conditional and simple discrimination performance, body weight and body composition was assessed at regular intervals over a period of 14 weeks. For data analysis, each diet group was stratified by median body fat percentage. For the hippocampal-dependent feature negative task, among those with <50th% for body fat, the rats receiving chow significantly outperformed the other groups. However, among those ≥50th% for body fat, the WD + MSG group significantly outperformed the other 3 groups (p=0.01). For the non-hippocampal dependent simple discrimination task, among animals <50th% for body fat, no differences were noted between groups. However, among those ≥50th% for body fat, the WD MSG group had the highest performance, though not meeting significance (p<0.10). The improved hippocampal performance in overweight rats in this study receiving the WD+MSG diet could be due to enhanced gluconeogenesis in the brain (with conversion of glutamate to alpha-ketoglutarate in the Krebs cycle). This research could inform future work on obesity related cognitive dysfunction. More research is needed to fully understand brain gluconeogenesis and whether increased intake of certain dietary amino acids may be able to improve brain energy production in obesity.

Funding Source: Faculty Research Support Grant from American University

CoAuthors: Sara Hargrave, PhD – NIH; Terry Davidson, PhD – American University

Kathleen F. Holton

Asst. Professor
American University
Washington, District of Columbia