Cocaine directly augments the alpha-adrenergic contractile response of the pregnant rabbit uterus.
Cocaine use in pregnancy is associated with a premature labor rate as high as 50%, but little is known about its effect on uterine contractility. To determine whether cocaine directly augments pregnant uterus contractility, uterine strips from 27-day pregnant New Zealand White rabbits (term, 31 days) were exposed to cocaine alone (30 mumol/L) or cocaine plus epinephrine (10(-9) to 10(-5) mol/L) or oxytocin (10(-10) to 10(-6) mol/L). Cocaine alone produced no contractions, but increased the epinephrine sensitivity by 51% and the maximal response by 33%. When beta-adrenoceptors were blocked with DL-propranolol (2 mumol/L), the contractile response to epinephrine was increased, and cocaine's effect was blocked. In the presence of the stereoisomer D-propranolol (2 mumol/L) with no beta-adrenergic antagonist activity, the contractile response to epinephrine was unchanged, but the effect of cocaine was still blocked. We conclude that cocaine directly augments the alpha-adrenergic contractile response of the pregnant rabbit uterus by a mechanism that is blocked by the non-beta-adrenergic effects of propranolol.
Hurd
W W
WW
Department of Obstetrics, Gynecology and Reproductive Sciences, University of California, San Francisco.
Robertson
P A
PA
Riemer
R K
RK
Goldfien
A
A
Roberts
J M
JM
D000319:Adrenergic beta-Antagonists / Q000494:pharmacology; D000818:Animals; D003042:Cocaine / Q000494:pharmacology*; D004837:Epinephrine / Q000494:pharmacology; D005260:Female; D011247:Pregnancy; D011270:Pregnancy, Animal; D011433:Propranolol / Q000494:pharmacology; D011817:Rabbits; D011942:Receptors, Adrenergic, alpha / Q000502:physiology*; D013237:Stereoisomerism; D014590:Uterine Contraction / Q000187:drug effects* / Q000502:physiology
D000319:Adrenergic beta-Antagonists; D011942:Receptors, Adrenergic, alpha; D011433:Propranolol; D003042:Cocaine; D004837:Epinephrine