Catecholamine turnover in heart and adrenals of young rats: effects of rearing temperature.

1. A comparative chronological study (from birth to one month of age) was performed to establish the levels and turnover rates of catecholamines in the heart and adrenals of rats born and reared at 28 and 16 degrees C. 2. In the heart, cold induced marked increases of the norepinephrine level and turnover rate only from the second week of age. 3. In the adrenals there was considerable early stimulation of epinephrine production, but only in 28 degrees C rats. 4. The differences observed in the stimulation of the sympathetic nervous system according to the rearing temperature are possibly due to the behavior of the mother in warming the pups.