Prenatal cocaine exposure affects the development of aortic adrenergic innervation and contractile responses

Blockade of noradrenaline transport abolishes 4-methylthioamphetamine-induced contraction of the rat aorta in vitro

The aim of this study was to characterize the effects of 4-methylthioamphetamine (4-MTA) on contractility and noradrenaline (NA) transport and release in the isolated rat aorta. Descending thoracic aortic rings were isolated from male Wistar rats (220-240 g) and the effect of 4-MTA on contractility was measured by isometric force displacement. 4-MTA (0.1 microm-1 mm) induced a concentration-dependent contraction of aortic rings, with a pD(2) of 4.40 +/- 0.38, and an E(max) of 0.80 +/- 0.05 g tension. The alpha(1)-adrenoceptor antagonist, prazosin (1 microm) and alpha(2) antagonist, yohimbine (1 microm) inhibited maximal contraction to 100 microm 4-MTA by 45.0 +/- 6.7% and 53.5 +/- 7.1% of control values respectively, whereas the 5-hydroxytryptamine (5-HT) antagonist, ketanserin (100 nm) had no effect on the 4-MTA-mediated contraction. The specific NA transport inhibitor, nisoxetine (1 microm) abolished contraction of the aorta by 4-MTA. 4 Nisoxetine-sensitive [(3)H]-NA transport in aortic rings was measured over a concentration range of 0-5 microm [(3)H]-NA, and had a maximal rate of transport (V(max)) of 0.77 +/- 0.07 pmol [(3)H]-NA min(-1) mg(-1) protein and a Michaelis affinity constant (K(M)) of 2.3 +/- 0.5 microm. 4-MTA inhibited nisoxetine-sensitive [(3)H]-NA transport with a pIC(50) of 6.16 +/- 0.18 and the pIC(50) for inhibition of nisoxetine-sensitive [(3)H]-NA transport by 3,4-methylenedioxymethamphetamine (MDMA) was 6.83 +/- 0.13. 4-MTA (1-100 microm) significantly stimulated release of pre-loaded [(3)H]-NA from aortic rings and 4-MTA-induced [(3)H]-NA release was inhibited by 1 microm nisoxetine. These data suggest that 4-MTA causes contraction of the rat aorta in vitro by a mechanism that is consistent with an ability to cause release of NA at the level of the NA transporter. It is concluded that 4-MTA has the potential to increase the extracellular concentration of NA peripherally as well as centrally, and that this may cause adverse cardiovascular effects in its users.

Cardiovascular effects of acute and chronic cocaine administration in pregnant and nonpregnant rabbits

The effects of cocaine administration on cardiovascular parameters were studied in anesthetized nonpregnant and pregnant rabbits with no prior exposure to cocaine and in pregnant rabbits repeatedly administered cocaine (4 mg/kg, bid, iv) for 15-20 days prior to the experiment. Rabbits were instrumented to determine the effects of cocaine on blood pressure, heart rate, and organ blood flows. Administration of the 1 and 2 mg/kg doses of cocaine increased blood pressure and decreased heart rate in both pregnant and nonpregnant rabbits. In contrast, the 4 mg/kg dose of cocaine caused reductions in both blood pressure and heart rate. Cocaine (1, 2, and 4 mg/kg, iv) also caused dose-dependent reductions in organ blood flows. Interestingly, cocaine did not affect uterine blood flow in the nonpregnant rabbits, whereas uterine and placental flows were markedly reduced in both groups of pregnant rabbits. Chronic treatment with cocaine caused a significant increase in the basal blood flow to the placenta and spleen, and a more precipitous decrease in blood flow in both organs in response to an acute injection of cocaine. The chronically treated rabbits also had a greater incidence of cardiac arrhythmias in response to an acute injection of cocaine (4 mg/kg, iv). Rabbits that received repeated administrations of cocaine experienced more prolonged reductions in blood flow than rabbits with no prior exposure to cocaine. These studies show that cocaine has marked effects on organ blood flows and that pregnancy and repeated prior administrations of cocaine can enhance these effects.