Abstract
To test the possible role of biogenic amines as neurotransmitters in thermoregulation, norepinephrine, epinephrine, 5-HT, and dopamine were infused into the anterior hypothalamus or third ventricle of the brain of conscious baboons. Norepinephrine infused at 1 µg/min for 15 min evoked cutaneous vasodilation, bradycardia, hypotension, and a 1.2°C (SE) fall in mid-brain temperature (Tmb), used as an index of core temperature, within 1 h (p<0.005). Baboons shivered and cutaneous vasoconstriction was evident within 1.5 h; Tmb returned to normal within 3.5 h. Heart rate, blood pressure and urinary catecholamine excretion rose during shivering thermogenesis. Plasma glycerol and glucose also rose during this interval, but plasma 17-hydroxycorticoids and serum growth hormone did not change. In contrast to this evidence, 5-HT did not mediate heat gain. Hypothalamic infusion of either epinephrine or dopamine caused no change in Tmb, but dopamine lowered serum growth hormone.
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