Endogenous catecholamines augment the inhibitory effect of opioids on luteinizing hormone secretion during the midluteal phase.
OBJECTIVE
Our purpose was to test the hypothesis that endogenous catecholamines may interact with endogenous opioid peptides to influence gonadotropin secretion during the midluteal phase in normal women.


METHODS
Normal cycling women studied during the midluteal phase were randomized to one of four treatment groups: (1) alpha-methyl-para-tyrosine, (2) naloxone, (3) alpha-methyl-para-tyrosine and naloxone, and (4) control. Mean treatment luteinizing hormone levels were compared by analysis of variance. Pulse frequency, amplitude, and integrated area under the curve were assessed by CLUSTER analysis and compared by means of nonparametric analyses.


RESULTS
Mean luteinizing hormone levels were significantly higher in the naloxone and alpha-methyl-para-tyrosine plus naloxone groups compared with alpha-methyl-para-tyrosine or placebo. Coadministration of alpha-methyl-para-tyrosine and naloxone caused a significant increase in large-burst luteinizing hormone pulses compared with the group receiving naloxone only.


CONCLUSIONS
Endogenous catecholamines augment the inhibitory effect of opioids on luteinizing hormone secretion during the midluteal phase in normal cycling women.
Fujimoto
V Y
VY
Department of Obstetrics, Gynecology and Reproductive Sciences, University of California, San Francisco 94143-0132.
Spencer
S J
SJ
Rabinovici
J
J
Plosker
S
S
Jaffe
R B
RB
D000293:Adolescent; D000328:Adult; D000704:Analysis of Variance; D002395:Catecholamines / Q000502:physiology*; D016000:Cluster Analysis; D004311:Double-Blind Method; D004357:Drug Synergism; D004723:Endorphins / Q000502:physiology*; D005260:Female; D006801:Humans; D008183:Luteal Phase / Q000097:blood / Q000502:physiology*; D007986:Luteinizing Hormone / Q000097:blood / Q000378:metabolism*; D008781:Methyltyrosines / Q000494:pharmacology; D009270:Naloxone / Q000494:pharmacology; D011388:Prolactin / Q000097:blood; D014446:Tyrosine 3-Monooxygenase / Q000037:antagonists & inhibitors; D019805:alpha-Methyltyrosine
D002395:Catecholamines; D004723:Endorphins; D008781:Methyltyrosines; D009270:Naloxone; D019805:alpha-Methyltyrosine; D011388:Prolactin; D007986:Luteinizing Hormone; D014446:Tyrosine 3-Monooxygenase