Cocaine acutely increases rat myometrial contractile activity by mechanisms other than potentiation of adrenergic pathways.
OBJECTIVE
We hypothesized that cocaine acutely increases contractile activity in isolated rat myometrium and that this effect is solely caused by potentiation of adrenergic pathways.


METHODS
Isometric contractions were measured in myometrium isolated from virgin and day-18 pregnant Sprague-Dawley rats. Frequency, duration, amplitude, and integrated area were compared before and after the addition of cocaine (10(-6) to 10(-4) mol/L) by means of analysis of variance and Duncan's multiple-range test. The effects of alpha-adrenergic receptor antagonists (prazosin 10(-6) mol/L and yohimbine 10(-6) mol/L) and beta-adrenergic receptor antagonist (DL-propranolol 2 x 10(-6) mol/L) were assessed.


RESULTS
Contraction duration, expressed relative to control, increased acutely after cocaine (10(-5) mol/L) administration in pregnant (1.70 +/- 0.20) and nonpregnant (1.36 +/- 0.24) myometrium (mean +/- SE, p < 0.05), as did integrated area (pregnant 3.47 +/- 0.97, nonpregnant 2.48 +/- 0.66) (mean +/- SE, p < 0.05). These effects were not completely inhibited by adrenergic blockade.


CONCLUSIONS
Cocaine acutely increases the duration and integrated area of spontaneous contractions in isolated rat myometrium by mechanisms not completely explained by inhibition of catecholamine reuptake and potentiation of adrenergic pathways.
Monga
M
M
Department of Obstetrics, Gynecology, and Reproductive Sciences, University of Texas Medical School at Houston 77030.
Weisbrodt
N W
NW
Andres
R L
RL
Sanborn
B M
BM
D000818:Animals; D002395:Catecholamines / Q000502:physiology; D003042:Cocaine / Q000494:pharmacology*; D005260:Female; D066298:In Vitro Techniques; D009215:Myometrium / Q000187:drug effects* / Q000502:physiology; D011224:Prazosin / Q000494:pharmacology; D011247:Pregnancy; D051381:Rats; D017207:Rats, Sprague-Dawley; D011942:Receptors, Adrenergic, alpha / Q000187:drug effects*; D012110:Reserpine / Q000494:pharmacology; D014590:Uterine Contraction / Q000187:drug effects* / Q000502:physiology; D015016:Yohimbine / Q000494:pharmacology
D002395:Catecholamines; D011942:Receptors, Adrenergic, alpha; D015016:Yohimbine; D012110:Reserpine; D003042:Cocaine; D011224:Prazosin