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Suppression of feeding by the glutamate receptor antagonist DAP-5 in the sensory specific satiety model of overeating in rats.

Palatability of food is a biobehavioral factor that facilitates overeating (McCrory, et. al., J. Nutrition, 2002). An animal model for overeating, known as sensory specific satiety (SSS), demonstrates that satiated rats offered a second meal will eat sooner and will increase consumption when presented with a new, more palatable food. Conversely, rats will eat less if presented with the same food again. Previous studies suggest that neural activity at glutamate receptors in the lateral hypothalamus (LH) may regulate overeating during SSS. We hypothesized that overeating can be suppressed during SSS by LH injection of DAP-5, a glutamate receptor antagonist for the NMDA receptor subtype. Cannulas were implanted into the rats' LH via stereotaxic surgery (N=14). Once fed to satiety on a first meal of chow, the rats received a 0.3[micro]L injection of DAP-5 [doses = 0 (control) & 10 nmol, counterbalanced] into the LH and were presented with a second meal of either chow or Kellogg's Froot Loops[R]. Measurements of cumulative food intake (g) and latency to feed (min), the amount of time taken to initiate feeding, were recorded and analyzed. Under control conditions, rats ate significantly more Froot Loops[R] (1.6 [+ or -] 0.28 g) than chow (0.29 [+ or -] 0.28 g) in the second meal (p<0.05, by ANOVA and Student Newman Keuls). However, injection of DAP-5 suppressed SSS as indicated by comparable consumption of chow (0.02 [+ or -] 0.28 g) and Froot Loops[R] (0.6 [+ or -] 0.28 g) during the second meal (p=0.14). In addition, the latency to feed post-injection was not significantly different for chow (46.2 [+ or -] 4.3 min) as compared to Froot Loops[R] (34.3 [+ or -] 4.3 min), suggesting that SSS was suppressed (p=0.06). In summary, rats fed to satiety on chow will eat less during a second, more palatable meal when treated with the glutamate receptor antagonist, DAP-5. These data suggest that activation of the NMDA subtype of glutamate receptors within the LH regulates some aspect of overeating.
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Author:Laser, K.S.; Saine, E.B.; Stinnett, T.S.; Yanke, A.B.; Hettes, S.R.
Publication:Bulletin of the South Carolina Academy of Science
Date:Jan 1, 2005
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