Preference for a solution of branched-chain amino acids plus glutamine and arginine correlates with free running activity in rats: involvement of serotonergic-dependent processes of lateral hypothalamus.

Rats were given free access to a running wheel, food, water, and a solution composed of branched-chain amino acids plus glutamine and arginine (the "BCAA-based" solution). A positive relationship between dark-period running distance and preference for the BCAA-based solution was observed. Serotonin release in the lateral hypothalamus, the central nucleus of amygdala and the medial nucleus raphe in overnight fluid-deprived rats during their first subsequent free drinking was also measured. A lowered serotonin release in the lateral hypothalamus characterized the rats that consumed the BCAA-based solution. No drink-related changes were observed in the amygdala. A separate group of rats was trained on a treadmill. Following the training period, plasma amino acids and brain serotonin release were measured during running. The BCAA-based solution infused before running elevated the branched chain amino acids/tryptophan plasma ratio at the end of, and after, running. Additionally, a decreased lateral hypothalamus serotonin release was seen 80 min after running, when compared with water-infused rats. No fluid-related changes in the amygdala were observed. The exercise-related shift in the fluid preference towards a BCAA-based solution suggests an ergogenic benefit. The forced-running study shows the lateral hypothalamus as a critical region in the effects of a BCAA-based solution.