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 °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.