Quantifying nonlinear interactions within the hypothalamo-pituitary-adrenal @entity2270 in the conscious XXXX .

@entity1831 @entity1641 @entity69139 @entity5463 @entity701 @entity2270
@entity701 is an important mediator of physiological stress responses. Hypothalamic @entity69139 and @entity5463 ( @entity1831 ) and pituitary ACTH, in addition to hypothalamic and pituitary @entity701 feedback, regulate @entity701 secretion. Importantly, joint interactions among the four, rather than the signal of any one hormone, govern this life-preserving @entity2270 . Quantifying in vivo strength of such joint interactions has been difficult, especially without direct injection of @entity701 , @entity69139 , AVP, or ACTH. The goal of the present research was to estimate these joint feedback and feedforward interactions in vivo in the conscious @entity1641 during low- @entity701 and hypoglycemic stress. Pituitary venous sampling of ACTH, @entity69139 , and AVP was performed every 0.5-1 min and jugular venous sampling of @entity701 every 15-20 min. Estimation of hypothalamic dynamics revealed that: 1) hypocortisolemia amplifies @entity69139 and AVP secretion, when mean (slow) and rate-adjusted (rapid) @entity701 feedback concentrations decrease by 0-25%; and 2) reduced peptide feedback augments @entity69139 and AVP secretion, when @entity69139 and AVP secretion each decreases by 0-25 and 50% of its respective maximum. Thus, low- @entity701 feedback enhances @entity69139 outflow in part by relieving @entity69139 's autoinhibition. Estimation of pituitary dynamics disclosed that: 1) endogenous @entity69139 and AVP synergize in evoking ACTH secretion, and 2) hypocortisolemia potentiates individual and conjoint stimulation of ACTH secretion by @entity69139 and AVP. Formulations such as the present one should have application to evaluating other complex endocrine dynamics.
