to test the hypothesis that endogenous opioids participate in the regulation of the ontogenic development of the hypothalamic-pituitary-adrenal axis in fetal sheep , we measured changes in immunoreactive ( ir ) acth and cortisol concentrations in response to bolus injections of either the [ met ] -enkephalin analogue , [ d-ala2 , n-phe4 , met ( 0 ) ol5 ] -enkephalin ( fk 33-824 ; 25 micrograms ) , the opioid antagonist naloxone ( 1 mg ) , a combination of both , or saline vehicle , administered to chronically catheterized fetal sheep through late gestation .
C0014295
met
C0014298
enkephalin