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

Abstract

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.

Oral branched-chain amino acid supplements that reduce brain serotonin during exercise in rats also lower brain catecholamines

“…We used the amino acid pattern employed by Smriga et al (2002) to construct the amino acid solution administered as a BCAA mixture. They administered to rats per os a BCAA, glutamine, and arginine.…”

“…They administered to rats per os a BCAA, glutamine, and arginine. The solution consisted of (mmol/l): leucine (LEU) 15.2, isoleucine (ILE) 9.9, valine (VAL) 11.1, glutamine 16.6, and arginine 13.9 (Smriga et al 2002). The approximate weight of the rats was accessed by following the link in the citation at the bottom of the page.…”

“…In particular, we evaluated whether the administration of a mixture of BCAA used previously to block exercise-induced increases in brain 5HT in rats (Smriga et al 2002) would lower 5HT and catecholamines. As the outcome confirmed the hypothesis, we also examined if the inclusion of TYR with BCAA would block the BCAA effect on catecholamines.…”

“…We focused on hypothalamus in this study, as this region shows clear effects of each precursor on the production rate of the respective transmitter (Fernstrom and Fernstrom 1995b, c). Hypothalamus is also one of the brain regions in which 5HT release has been shown to be increased by exercise and blocked by BCAA (Smriga et al 2002). We studied 5HT and catecholamine synthesis rates, as synthesis reliably reflects neuronal release in amino acid experiments such as these (Gartside et al 1992;McTavish et al 1999;Rouch et al 2003).…”

“…A second EAA formulation was also tested, and was based in part on the EAA composition of a food (non-fat dry milk) (US Department of Agriculture, Agricultural Research Service 2006). This formulation employed LEU, ILE, VAL, arginine, and glutamine at the doses used by Smriga et al (2002), and standardized the doses of the other EAA to the LEU content of non-fat dry milk. The EAA composition of non-fat dry milk is (g/100 g food): LEU 3.48, ILE 2.15, VAL 2.38, histidine 0.96, lysine 2.82, methionine 0.89, PHE 1.71, TYR 1.60, and TRP 0.50 (US Department of Agriculture, Agricultural Research Service 2006).…”