dopamine levels in arterial plasma from the same rats were low or undetectable ( 0.4 -- 0.8 ng/ml1 . norepinephrine and epinephrine was undetectable ( less than 0.6 ng/ml ) in portal as well as arterial plasma from these rats . the major catecholamine in extracts of the hypothalamus from pregnant rats was norepinephrine , whereas that in the posterior pituitary was dopamine . dopamine levels in portal plasma collected during proestrus , estrus , diestrus 1 , and diestrus 2 , were 1.32 +/- 0.21 ( mean +/- se ) , 3.87 +/- 0.96 , 3.11 +/- 0.73 , and 2.3 +/- 0.45 , respectively . dopamine in portal plasma from intact and from castrated male rats was approximately 0.6 ng/ml . norepinephrine and epinephrine were not detectable in either portal or arterial plasma from these animals . it is concluded 1 ) that dopamine is secreted into hypophysial portal blood in significant quantities during pregnancy , 2 ) that hypothalamic secretion of dopamine in cyclic rats is greatest during the day of estrus and early diestrus and at least on the day of proestrus , and 3 ) that these findings support the view that dopamine of hypothalamic origin may have an important role in the regulation of anterior pituitary function .
C0007412
catecholamine
C0013030
dopamine