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. Author manuscript; available in PMC: 2013 Oct 23.
Published in final edited form as: Curr Biol. 2012 Sep 20;22(20):1918–1924. doi: 10.1016/j.cub.2012.08.014

Fig. 1. Endogenous extracellular opioid peptides in response to palatable food consumption.

Fig. 1

Extracellular enkephalin levels surged when rats began to eat milk chocolate M&Ms™. Onset of eating coincided with a robust increase in extracellular enkephalin (met and leu), which remained sustained during eating, and gradually tapered off as eating declined. The magnitude of the enkephalin rise in individuals correlated with their latency to eat their first M&M™: higher enkephalin rise for the fastest eaters. The correlation between faster speed to start eating and higher enkephalin also remains significant if the highest outlier individual (upper right of inset) is removed (spearman’s rho=−0.85, p=0.013, 95% CI [−1,−0.4]). * indicates p<0.05. Error bars represent standard error of the mean.