Inhibition of LH and prolactin release in the cycling rat following inhibition of dopamine-beta-hydroxylase.
The effect of fusaric acid, an inhibitor of dopamine-beta-hydroxylase (DBH), on luteinizing hormone (LH) and prolactin levels during the estrous cycle was determined. Fusaric acid was found to cause a selective dose- and time-dependent inhibition of DBH activity in the medial basal hypothalamus without altering tyrosine hydroxylase activity. When DBH was inhibited during the afternoon of diestrus, the proestrous surges of both LH and, to a lesser extent, prolactin were inhibited. These results suggest that noradrenergic neuronal activity in the mediobasal hypothalamus is required during the afternoon preceding proestrus in order for the LH and prolactin surges to occur. It is possible that the rise in serum estrogen during late diestrus 2 is blocked by fusaric acid treatment. This estrogen increase is necessary for LH and prolactin surges to occur during proestrus. When DBH was inhibited during the afternoon of proestrus, the LH and prolactin surges were completely eliminated. This indicates that noradrenergic neuronal activity in the mediobasal hypothalamus during the afternoon of proestrus is important for both the LH and prolactin surges to occur.
D000818:Animals; D004299:Dopamine beta-Hydroxylase / Q000037:antagonists & inhibitors* / Q000378:metabolism; D004971:Estrus / Q000187:drug effects*; D005260:Female; D005669:Fusaric Acid / Q000494:pharmacology; D007031:Hypothalamus / Q000187:drug effects / Q000201:enzymology; D007986:Luteinizing Hormone / Q000037:antagonists & inhibitors* / Q000097:blood; D011247:Pregnancy; D011388:Prolactin / Q000037:antagonists & inhibitors* / Q000097:blood; D051381:Rats; D014446:Tyrosine 3-Monooxygenase / Q000378:metabolism
D011388:Prolactin; D007986:Luteinizing Hormone; D014446:Tyrosine 3-Monooxygenase; D004299:Dopamine beta-Hydroxylase; D005669:Fusaric Acid