Stimulation of Growth Hormone Release by Microinjection of Norepinephrine into Hypothalamus of Baboons1

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Abstract
Serum growth hormone (GH) rose after norepinephrine (NE) was microinjected into or in the vicinity of the ventromedial nucleus (VMN) of the hypothalamus of three conscious baboons. Microinjections of NE (10 μg in 10 μl) elevated GH from control level of 4 ± 1 ng/ml to 22 ± 5 ng/ml (SEM) at 25 min (P < 0.025) and to 29 ± 10 ng/ml at 40 min (P < 0.010). GH thereafter declined exponentially (N = 6). Plasma 17-OHCS also rose significantly over the same time course, indicating pituitary ACTH release by NE injection into the VMN. The absence of concurrent changes in blood pressure, heart rate, plasma glucose, insulin, or glycerol indicates that the GH elevation was not a response to nonspecific stress or to alterations in circulating substrates. Rather, the data suggest that NE acts on the VMN to directly stimulate hypothalamic mechanisms regulating GH secretion. (Endocrinology90: 895, 1972)

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