Effect of acute and chronic elevated air temperatures, constant (34 degrees) and cyclic (10--34 degrees), on brain and heart norepinephrine of male Japanese quail.

Abstract

Abstract Endogenous levels and turnover of brain and heart norepinephrine (NE) of male quail ( Coturnix coturnix japonica ) were fluorometrically determined after exposure to either acute (6 hr) and chronic (5 week) 34° or cyclic temperature (10–34°) stress. α-Methyl- p -tyrosine (αMT) was used to induce depletion of endogenous norepinephrine levels by inhibition of tyrosine hydroxylase. The differences between the levels of treated and control birds (22°) were regarded as changes in turnover. High ambient temperature (34°) stress for 6 hr increased brain NE levels, decreased heart NE levels, and increased turnover of brain and heart NE. However, chronic exposure (5 weeks) to 34° and cyclic temperature (10–34°) did not increase turnover of brain NE, though chronic exposure to 34° increased heart NE turnover. The results indicate that there is increased noradrenergic activity during acute thermal exposure, and that after acclimation to thermal stress for 5 weeks, the noradrenergic activity declines in the brain, though it persists in the heart. Chronic exposure to 34° significantly reduced heart, adrenal, and testes weights, but exposure to chronic cyclic temperatures (10–34°) only reduced adrenal weight.