Effect of alpha1 receptor blockade upon maternal and fetal cardiovascular responses to cocaine

Article Abstract:

The adverse effects of cocaine abuse during pregnancy have been well documented. Cocaine can increase the mother's blood pressure, decrease the blood flow to the uterus and change the character of the blood flow by increasing the resistance through blood vessels. This in turn decreases the oxygen available to the fetus, and increases fetal blood pressure and heart rate. It is thought that cocaine causes these cardiovascular changes as it blocks the re-uptake of the neurotransmitting chemical norepinephrine within the nerve endings. This leaves norepinephrine to circulate in the blood, causing blood vessels to narrow, thus increasing blood pressure and decreasing blood flow. There are two cell receptors having a particular affinity for norepinephrine, alpha-1 and alpha-2. It is hypothesized that blocking alpha-2 receptors, which are involved in stimulating the contraction and narrowing of blood vessels, with the blocking agent phenoxybenzamine will prevent the circulating norepinephrine from constricting the blood vessels. The blocking action of phenoxybenzamine is irreversible, in that it prevents the receptors from ever being used again. In response to that blockade, new receptors are made. The effect of cocaine before and after phenoxybenzamine alpha-1 adrenergic receptor blockade was studied among four pregnant sheep and their fetuses. Before phenoxybenzamine, cocaine (2.0 milligrams per kilogram of body weight) increased maternal blood pressure by 53 percent, reduced blood flow to the uterus by 50 percent and increased the blood flow resistance by 191 percent. It also increased fetal blood pressure by 24 percent and fetal heart rate by 51 percent and reduced the concentration of oxygen in the blood of the fetus by 29 percent. After the administration of phenoxybenzamine (5.0 milligrams per kilogram of weight), cocaine failed to increase maternal and fetal blood pressure. The blood flow to the uterus was decreased by 44 percent, blood vessel resistance increased 59 percent, fetal heart rate increased 36 percent and the concentration of oxygen in the fetal blood decreased 18 percent. It is concluded that cocaine exerts its effects by attaching to the alpha-1 adrenergic receptors. The action of other neurotransmitter chemicals (dopamine or serotonin) may be involved in causing the decreased blood flow in the arteries supplying the uterus. (Consumer Summary produced by Reliance Medical Information, Inc.)

Models, Heart, Cocaine abuse, Noradrenaline, Norepinephrine, Antihypertensive agents, Adrenergic alpha blockers, Adrenergic alpha-antagonists, Phenoxybenzamine

---

Effects of repeated administration of cocaine to the fetal sheep in the last days of pregnancy

Article Abstract:

Daily cocaine abuse during late pregnancy may cause certain changes in the fetus. Among ten fetal sheep in the last days of gestation, five were injected intravenously with two milligrams of cocaine per kilogram of body weight each day over a 3- to 14-day period and five were not injected with cocaine. The amount of oxygen present in arterial blood was significantly lower in the fetuses injected with cocaine on the first day of treatment than in those not injected with cocaine. The fetuses injected with cocaine experienced significant decreases in blood pH and significant increases in blood levels of carbon dioxide. Both fetal heart rate and fetal blood pressure temporarily increased after injection of cocaine. Injection with cocaine also stimulated fetal breathing during delivery. Usually fetal breathing does not occur during labor and delivery.

---

Similar abstracts:

• Abstracts: Effect of octreotide on intestinal motility and bacterial overgrowth in scleroderma. Octreotide therapy for tumor-induced osteomalacia
• Abstracts: The temporal relationship between maternal blood and amniotic fluid glucose levels. Exercise prescription in pregnancy: weight-bearing versus non-weight-bearing exercise
• Abstracts: Aspirin for prevention of myocardial infarction and stroke. Aspirin for primary prevention of cardiovascular disease
• Abstracts: Optimal etching time of glass ionomer cement for maximum bond of composite resin. The glass ionomer cement
• Abstracts: Intralesion interferon alpha-2b for the treatment of genital warts. Combined interferon alfa and doxorubicin in the treatment of advanced cervical cancer

This website is not affiliated with document authors or copyright owners. This page is provided for informational purposes only. Unintentional errors are possible.