Tyrosine improves behavioral and neurochemical deficits caused by cold exposure

The effects of acute cold stress were assessed behaviorally and neurochemic ally. The norepinephrine (NE) precursor, tyrosine (TYR), the catecholamine- releasing compound, amphetamine (AMPH), and the adrenoceptor agonist, pheny lpropanolamine (PPA), were administered systemically either alone or in con junction with TYR 30 min prior to cold exposure. All three sympathomimetic treatments dose-dependently improved performance in a forced swim test fol lowing hypothermia (T-c = 30 degreesC). AMPH/TYR or PPA/TYR combinations fu rther improved performance vs, either agent given alone. Microdialysis show ed elevated hippocampal NE concentrations in response to hypothermia. TYR f urther elevated NE concentration in cold/restrained rats vs. saline (SAL)-t reated controls. These results suggest that sympathomimetic agents, includi ng the nutrient TYR, which enhance noradrenergic function, improve performa nce in animals acutely stressed by hypothermia. (C) 2001 Elsevier Science I nc. All rights reserved.