Negative feedback in adrenocortical response to limbic stimulation in Macaca mulatta

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Abstract
Negative feedback influence of circulating 17-hydroxycorticosteroids (17-OHCS) was sought in the adrenocortical response to limbic stimulation in conscious chair-confined Macaca mulatta. Intravenous injection of 1 mg of a soluble hydro-cortisone preparation increased plasma 17-OHCS concentration 10-15 [mu]g/100 ml 75 min. later. When this injection was given 15 min. before an hour of amygdaloid stimulation, total change in plasma 17-OHCS (23 + 11 [mu]g/100 ml (mean [plus or minus] SD)) was not different from that produced by 1 hr. of amygdaloid stimulation alone (24 [plus or minus] 8 [mu]g/100 ml). If the injection preceded 1 hr. of hypothalamic stimulation, total increase in 17-OHCS (45 [plus or minus] 7 ug/100 ml) was significantly larger (P < 0.01) than with hypothalamic stimulation alone (21 [plus or minus] 3 ''g/100 ml). These data are evidence for a negative feedback effect of injected hydrocortisone on the 17-OHCS response to amygdaloid stimulation but not to hypothalamic stimulation and suggest the presence of a neural mechanism for negative feedback located functionally between amygdala and hypothala-mus.