Pregnancy enhances cocaine-induced stimulation of uterine contractions in the chronically instrumented rat

Prostaglandin D2 evokes potent uterine contraction via the F prostanoid receptor in postpartum rats

Prostaglandin (PG) D₂, a prostanoid known to have hypotensive effect, can evoke increased in vitro prepartum myometrial contraction resulting from up-regulation of the F prostanoid (FP) receptor. The present study further determined postpartum rat uterine responses to PGD₂ to evaluate the possibility of the prostanoid becoming a therapeutic for postpartum uterine atony, a major cause of postpartum hemorrhage that can lead to maternal morbidity. In vitro and in vivo postpartum uterine responses to PGD₂ were determined and compared to those of prepartum rats. Here we show that in postpartum myometrial strips PGD₂ did evoke a contraction sensitive to FP receptor antagonism. Interestingly, this response was not only to a greater extent than that of prepartum rats, but also comparable with the contraction obtained with PGF_2α, a therapeutic for postpartum uterine atony but contradicted in conditions including hypertension. Indeed, PGD₂ was also found to cause increases of basal uterine contraction under in vivo conditions. Western blots revealed that the expression of FP receptors in postpartum myometrium was higher than that of prepartum rats. Moreover, we noted that the amount of PGD₂ produced in postpartum uteri, although lower than that of prepartum rats, was increased compared to non-pregnant conditions. These results thus demonstrate that due to a further up-regulation or high expression of myometrial FP receptors, PGD₂ can evoke potent uterine contraction postpartum, and hence the prostanoid, which is naturally synthesized in uterine tissues, could be a potential therapeutic for postpartum uterine atony, especially in settings, such as hypertension.

Effects of adlay hull extracts on uterine contraction and Ca2+ mobilization in the rat

Dysmenorrhea is directly related to elevated PGF(2alpha) levels. It is treated with nonsteroid antiinflammatory drugs (NSAIDs) in Western medicine. Since NSAIDs produce many side effects, Chinese medicinal therapy is considered as a feasible alternative medicine. Adlay (Coix lachryma-jobi L. var. ma-yuen Stapf.) has been used as a traditional Chinese medicine for treating dysmenorrhea. However, the relationship between smooth muscle contraction and adlay extracts remains veiled. Therefore, we investigated this relationship in the rat uterus by measuring uterine contraction activity and recording the intrauterine pressure. We studied the in vivo and in vitro effects of the methanolic extracts of adlay hull (AHM) on uterine smooth muscle contraction. The extracts were fractionated using four different solvents: water, 1-butanol, ethyl acetate, and n-hexane; the four respective fractions were AHM-Wa, AHM-Bu, AHM-EA, and AHM-Hex. AHM-EA and its subfractions (175 microg/ml) inhibited uterine contractions induced by PGF(2alpha), the Ca(2+) channel activator Bay K 8644, and high K(+) in a concentration-dependent manner in vitro. AHM-EA also inhibited PGF(2alpha)-induced uterine contractions in vivo; furthermore, 375 microg/ml of AHM-EA inhibited the Ca(2+)-dependent uterine contractions. Thus 375 microg/ml of AHM-EA consistently suppressed the increases in intracellular Ca(2+) concentrations induced by PGF(2alpha) and high K(+). We also demonstrated that naringenin and quercetin are the major pure chemical components of AHM-EA that inhibit PGF(2alpha)-induced uterine contractions. Thus AHM-EA probably inhibited uterine contraction by blocking external Ca(2+) influx, leading to a decrease in intracellular Ca(2+) concentration. Thus adlay hull may be considered as a feasible alternative therapeutic agent for dysmenorrhea.

The influence of route of administration on the acute cardiovascular effects of cocaine in conscious unrestrained pregnant rats

The intravenous route of administration, accessed via a subcutaneous vascular access port, has been recently suggested as an animal model for studying the developmental effects of maternal cocaine abuse in the pregnant and/or group-housed rat. The present study (1) assessed the cardiovascular effects of intravenous (IV) cocaine, delivered via bolus injection, in chronically catheterized near-term pregnant rats, and (2) compared the IV cardiovascular responses to those following cocaine delivered via the commonly employed subcutaneous (SC) and intragastric (IG) routes of administration. Pregnant gestation day 15 (GD15) young adult female Sprague-Dawley rats (n = 21) were anesthetized and catheters surgically implanted into the carotid artery, jugular vein, fundus of the stomach, and a subcutaneous pouch. On GD17-19, heart rate (HR) and mean arterial pressure (MAP) were assessed, using a within-subjects design, prior and subsequent to IV (3 mg/kg), IG (60 mg/kg), and SC (40 mg/kg) cocaine. An interval of 6 h separated IV and IG cocaine administration and an interval of 18 h separated IG and SC cocaine administration. The peak responses of HR (23% downward arrow) and MAP (37% upward arrow) following IV cocaine were noted within 0.5 min. In contrast, the peak responses of HR (4% downward arrow, 6% downward arrow) and MAP (2% upward arrow, 15% downward arrow) after IG (23 min) or SC (26 min) cocaine, respectively, were significantly smaller and markedly delayed. No significant change in aortic blood flow velocity was detected following cocaine via any route of administration, although phasic flow velocities (PFV) were differentially sensitive to route of administration (PFV(dias) not PFV(sys)); IV cocaine increased (55% upward arrow) whereas IG or SC cocaine decreased approximately 35% downward arrow) PFV(dias). The pressor effects of an equimolar dose of IV cocaine methiodide (3.9 mg/kg) were indistinguishable from those of IV cocaine (38% upward arrow vs. 37% upward arrow), as were the effects on PFV(dias) (83% upward arrow vs. 55% upward arrow). The lack of an effect of cocaine methiodide on HR was consistent with the bradycardia effect of cocaine attributable to central mediation of the baroreflex. Finally, the pressor effects of IV cocaine paralleled the rapidly peaking arterial plasma levels of cocaine noted within 30 s after the initiation of drug injection. In sum, prominent effects of IV cocaine on maternal cardiovascular physiology are noted; as such, the recent reports of a lack of maternal/fetal toxicity following daily (3-6mg/kg) IV cocaine during GD8-21 are not due to use of an ineffective drug dose. It was equally clear that the SC and IG routes of exposure did not reproduce the cardiovascular component(s) of the expected physiological response to cocaine.

Long-term intravenous perinatal cocaine exposure on the mortality of rat offspring

To examine the effects of chronic perinatal cocaine exposure, cocaine was administered intravenously throughout pregnancy and the postpartum period to the rat. Pregnant rats were divided into five groups: nontreated (naive); normal saline control (saline); cocaine first generation (cocaine); saline in the first generation and cocaine in the second generation (Sal-2G); and cocaine in both first and second generations (Coc-2G). The rats receiving cocaine in the second generation (Sal-2G and Coc-2G) were offspring of the saline and cocaine group, respectively. All cocaine-treated groups received cocaine 2 mg/kg/day intravenously (IV), and the saline group received normal saline 0.2 ml/day IV from GD 2 to the 21st day postpartum. Mean perinatal mortality was greater in all pups exposed to cocaine in utero during gestation; Cocaine (6.4%); Sal-2G (5.6%); Coc-2G (11.4%) groups than in the noncocaine groups (3.2%, 1.3%). Weight gain, physical, and neurological developments of the offspring were not affected. It was concluded that perinatal cocaine exposure had an increased perinatal mortality even at doses approximately 10 times lower than those previously reported, which were administered by extravascular routes. These findings indicate the importance of the route of drug administration in perinatal cocaine research.