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Rats were placed at 28C for a control period of 4 hr prior to treatment with mecamylamine or saline. After injection the rats were divided into two groups with one group remaining at 28C and the other being placed at 15C. Ganglionic blockade with mecamylamine decreased the urinary excretion of norepinephrine and normetanephrine in both groups of rats. 3-methoxy-4-hydroxyphenyl glycol (MHPG) excretion fell in the mecamylamine-treated group kept at 28C but rose slightly in the group transferred to 15C. The fall in norepinephrine and normetanephrine excretion, seen after mecamylamine treatment, reflects a decrease in norepinephrine secretion. The increase in MHPG in the cold indicates a rise in the synthesis and intraneuronal degradation of norepinephrine. These results support our earlier postulate that the rate of norepinephrine synthesis is dependent, at least partially, on the ambient temperature and can dissociate itself from the rate of secretion. (Author)

The study demonstrates the influence of ambient temperature on the excretion of epinephrine, norepinephrine, and their major metabolites. As a result of this work it is concluded that norepinephrine secretion increases in a cold environment and decreases during moderate warm exposure. Heat stress, 36 C, however, increases norepinephrine excretion. The rate of norepinephrine synthesis is inversely proportional to the ambient temperature and in three instances in our experiments the quantity of amine formed was not related to the amount secreted. It is thus concluded that the rate of norepinephrine synthesis is dependent, at least partially, on the ambient temperature and can dissociate itself from the rate of norepinephrine secretion. (Author)