Tyrosine ameliorates heat induced delay in event related potential P300 and contingent negative variation

The efficacy of tyrosine, a catecholamine precursor, as a countermeasure in the reduction of cognitive decline during heat exposure (HE) using event-related potential P300, and contingent negative variation (CNV) was evaluated. Ten healthy males, age 20-30 years participated in the study. Volunteers received placebo or tyrosine (6.5 g) 90 min prior to HE (1.5 h in 45 degrees C + 30% RH). P300 latency was significantly increased (p < 0.01) during exposure with placebo, which was reduced significantly (p < 0.01) after tyrosine supplementation. There was an increase in CNV M100 latency (p < 0.05) and reaction time (p < 0.01) and decrease in M100 amplitude (p < 0.01) during HE with placebo, which returns to near normal level with the tyrosine administration. A significantly higher plasma norepinephrine (p < 0.05), dopamine and epinephrine levels were detected in tyrosine supplemented group post heat exposure. HE increases the brain catecholamine activity thereby reduces the plasma norepinephrine and dopamine level leading to a reduction in cognitive performances. Tyrosine supplementation increases the catecholamine level and reduces the impairment of cognitive performance during HE. (C) 2013 Elsevier Inc. All rights reserved.