Changes in sympathetic nerve terminals in the heart of cold-exposed rats.
Changes in sympathetic nerve terminals of the heart after varying periods of exposure of rats to 4 degrees C were investigated. Two indices were used for changes in the number of noradrenaline storage vesicles, i.e., vesicular dopamine beta-hydroxylase (DBH) activity and noradrenaline storage capacity. The latter was obtained after uptake of [3H]noradrenaline; endogenous content, uptake of exogenous noradrenaline, and degree of saturation of the vesicles were calculated using the specific activity of the [3H]noradrenaline. As a measure of tyrosine hydroxylase activity, whole ventricular noradrenaline, dopamine, and dihydroxyphenylacetic acid content were used. After 4 h of cold exposure there was an increase in vesicular endogenous noradrenaline content, uptake, storage capacity, and DBH activity as well as a large increase in whole ventricular dopamine. After 6 h in the cold, vesicular endogenous noradrenaline content, storage capacity, and DBH activity were decreased. The results suggest that during cold exposure there is an initial increase followed by a decrease in the number of functional vesicles in the nerve terminal, which could explain the fluctuations in the rate of noradrenaline release.
University Laboratory of Physiology, Oxford, England.
M
M
Fillenz
S C
SC
Stanford
B G
BG
Coles
D015102:3,4-Dihydroxyphenylacetic Acid / Q000378:metabolism; D000818:Animals; D003080:Cold Temperature; D004298:Dopamine / Q000378:metabolism; D004299:Dopamine beta-Hydroxylase / Q000378:metabolism; D006329:Heart Conduction System / Q000378:metabolism*; D008297:Male; D009411:Nerve Endings / Q000378:metabolism*; D009638:Norepinephrine / Q000378:metabolism; D009994:Osmolar Concentration; D051381:Rats; D017207:Rats, Sprague-Dawley; D017208:Rats, Wistar; D013564:Sympathetic Nervous System / Q000378:metabolism*
D015102:3,4-Dihydroxyphenylacetic Acid; D004299:Dopamine beta-Hydroxylase; D004298:Dopamine; D009638:Norepinephrine