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The present experiment examined the developmental neurotoxicity of pulsed-wave (pw) ultrasound in rats, using an exposure system designed to eliminate restraint or anesthesia from the exposure conditions. Pregnant Sprague-Dawley CD rats trained to remain immobile in a water-filled ultrasound exposure tank were scanned with 3-MHz pw ultrasound at spatial peak temporal average intensities (ISPTA) of 0, 2, 20, or 30 W/cm2 on embryonic days 4-20 for approximately 10 min/day. The data showed that such insonation produced no adverse effects on maternal weight gain or reproductive outcome, nor on the postnatal growth or survival of the offspring. No exposure-related alterations in behavioral development were observed in the offspring of rats scanned with pw ultrasound during gestation. In addition, there was no consistent evidence of an ultrasound-associated change in the adult offspring behaviors tested; i.e., no treatment effects were found on measures of locomotor activity, water maze learning, and acoustic startle reactivity. An effect on tactile startle was observed on some trials in the low exposure group male offspring, but this effect was neither dose dependent nor consistent with any other finding. Overall, these results indicate that the neurobehavioral development of rats was not altered by prenatal exposure to pw ultrasound at ISPTA levels of up to 30 W/cm2.

While there are no known risks associated with diagnostic ultrasound, uncertainty about the safety of prenatal ultrasound exposure remains. The purpose of the present experiment was to evaluate the behavioral teratogenic potential of continuous-wave (cw) ultrasound in rats, in the absence of maternal anesthesia or restraint. Pregnant CD rats, trained to remain immobile in a water-filled ultrasound exposure tank, were scanned with 3 MHz cw ultrasound at levels of 0, 2, 10, 20, or 30 W/cm2 ISPTA (spatial peak, temporal average intensity) on gestational days 4-20 for approximately 10 min/day. Offspring were examined postnatally for survival, growth, physical landmarks of development, behavioral development, and the adult functions of locomotor activity, learning and memory, and startle reactivity. No effects of prenatal ultrasound were found on maternal characteristics, offspring survival or growth, physical or behavioral landmarks of development, or adult tests of passive avoidance or startle. Effects at the highest intensity were obtained on corner and side locomotor activity and in a multiple-T water maze on measures of errors of commission and time spent finding the goal. The results showed that prenatal cw ultrasound in rats can induce effects on some postnatal neurobehavioral functions at high exposure intensities (30 W/cm2), but at lower intensities (2-20 W/cm2) no consistent evidence of neurobehavioral effects was observed.

Although animal experiments have shown the trans-2-ene metabolite (t-2-ene-VPA) of valproic acid (VPA) to be pharmacologically equivalent to the parent compound in terms of anticonvulsant activity, it is considerably less teratogenic in studies which have examined prenatally exposed fetuses for morphological defects. This has made t-2-ene-VPA an attractive potential antiepileptic agent. However, while neurobehavioral alterations have also been observed in rats prenatally exposed to VPA, even at doses below those which produce malformations, the developmental neurotoxicity of t-2-ene-VPA had not previously been examined. The current study evaluated the long-term behavioral effects of prenatal exposure to t-2-ene-VPA. Pregnant CD rats were treated with 300 or 400 mg/kg t-2-ene-VPA by gavage on days 7-18 of gestation, doses previously shown to produce no teratogenicity. A VPA group was administered 300 mg/kg for comparison. The pharmacokinetic profiles of the two compounds were similar. Behavioral findings in offspring prenatally exposed to VPA were consistent with previous findings, i.e., VPA offspring exhibited decreased locomotor activity, increased swimming maze errors, and reduced tactile startle responding compared to controls. In the 400 mg/kg t-2-ene-VPA group, Cincinnati maze errors and auditory startle reactivity were increased, while no significant behavioral effects were detected in the 300 mg/kg t-2-ene group. These results indicate that the developmental neurotoxicity of t-2-ene-VPA is lower than that of VPA but is still significant.

To test the hypothesis that cocaine-induced embryonic vascular disruption is mediated by oxygen free radicals, the antioxidants 2-oxothiazolidine-4-carboxylate (OTC) and alpha-phenyl-N-t-butyl nitrone (PBN) were employed. When cocaine (78 mg/kg) was administered on day 8 of gestation to ICR mice and embryos evaluated on day 10 (in vivo), 62.3% of cocaine-treated embryos showed increased vasodilation compared to 4.9% for controls, and 33.1% of the cocaine-exposed embryos showed marked hemorrhage compared to 3.3% for controls. In addition, cocaine increased the incidence of neural defects, in the form of open neural tube, hypoplastic prosencephalon, and microcephaly. Administration of OTC (0.25 and 0.5 mmol/kg) or PBN (300 mg/kg) prior to cocaine significantly reduced cocaine-induced vasodilation and hemorrhage, while not preventing neural defects. When cocaine (78 mg/kg) was administered in vivo on day 8 of gestation and embryos were dissected 15 min later and subsequently cultured for 48 hr in the absence of cocaine (in vivo-in vitro), marked vascular disruption was observed: normal yolk circulation/heartbeat was decreased to 26.6%, while edema/blisters and vasodilation/hemorrhage were increased to 45.6% and 59.6%, respectively. Administration of PBN (300 mg/kg) prior to cocaine completely prevented cocaine-induced vascular disruption. When cocaine was administered in vivo and PBN (300 micrograms/ml) was incubated with cultured embryos in vitro, the antioxidant only partially prevented cocaine-induced cardiovascular defects in this model. Neural defects produced by cocaine were not significantly affected by PBN, administered either in vivo or in vitro. Cocaine (78 mg/kg) administered in vivo stimulated lipid peroxidation maximally after 3 hr in both day 8 and day 9 embryos. When cocaine was incubated in vitro during embryo culture at 33 micrograms/ml, a concentration that produces nonspecific inhibition of growth and development, embryonic lipid peroxidation on day 9 was not affected. Finally, when PBN (300 mg/kg) was administered prior to cocaine (78 mg/kg) on day 8 of gestation, stimulation of lipid peroxidation by cocaine was prevented. These results suggest that cocaine-induced vascular disruption in early development is mediated by maternal production of oxygen free radicals.

The purpose of this study was to determine whether vascular disruption is a feature of cocaine-induced teratogenicity in early murine organogenesis. The embryotoxic effects of cocaine were assessed: (1) in vivo, (2) in embryos cultured in the presence of cocaine (in vitro), and (3) after cocaine was administered in vivo and the embryos subsequently cultured in the absence of cocaine (in vivo-in vitro). When cocaine (78 mg/kg) was administered in vivo on day 8 and embryos were assessed on day 10, significant vascular perturbations, in the form of vasodilation and hemorrhage, as well as neural defects, were observed. In the in vitro system, day 8 embryos were cultured for 48 hr in the presence of 0, 10, 20, 33, and 66 micrograms/ml cocaine. At 10 and 20 micrograms/ml, vascular perturbation was not seen, while at higher cocaine concentrations, development of the yolk sac vasculature was inhibited. Hemorrhage was not a feature of in vitro cocaine embryotoxicity. However, significantly increased incidences of neural defects were seen at concentrations of 20 micrograms/ml or greater. Finally, in the in vivo-in vitro system, 78 mg/kg cocaine was administered on day 8 in vivo and embryos were dissected after 15 min and cultured for 48 hr. Marked cardiovascular perturbation, as well as neural defects, were produced using this protocol. With cocaine treatment, only 26.6% of embryos had a functioning heartbeat and yolk sac circulation, compared to 85.6% of controls. This cardiovascular disruption was associated with pooling of blood in the embryo, with 59.9% of embryos exhibiting marked vasodilation and hemorrhage compared to 12.5% in controls. Additional manifestations of cardiovascular perturbation were edema and blisters observed in cocaine-treated embryos. Neural tube defects, including open neural tube (8.3%) and microcephaly/hypoplastic prosencephalon (30.0%), were also significantly increased in cocaine-treated embryos. The cardiovascular and neural effects produced by cocaine were dose-dependent (40, 20 mg/kg). Thus, administration of cocaine in the in vivo or in vivo-in vitro systems produced marked cardiovascular effects, while in vitro treatment did not. These results suggest that cocaine may elicit cardiovascular toxicity through a maternally mediated mechanism.

While there are no known risks associated with diagnostic ultrasound, uncertainty about the safety of prenatal ultrasound exposure remains. The purpose of the present experiment was to evaluate the teratogenic potential of pulsed-wave (pw) ultrasound in rats, in the absence of maternal anesthesia or restraint. Pregnant CD rats, trained to remain immobile in a water-filled ultrasound exposure tank, were scanned with 3-MHz pw ultrasound at levels of 0, 2, 20 or 30 W/cm2 ISPTA (spatial peak, temporal average intensity) on gestational days 4-19 for approximately 10 min/day. Examination of fetuses on E20 revealed no increase in skeletal or visceral malformations in groups exposed to pw ultrasound in utero. The number of implantations/dam was significantly increased in all pw ultrasound exposure groups compared to sham-exposed animals and, in a possibly related finding, resorptions were increased in the two highest exposure groups. Although significantly increased compared to controls, resorption frequencies in these groups were low (< 10%). No exposure-related changes in fetal weights were observed in offspring of rats scanned with pw ultrasound during gestation. The results indicate that, under the conditions described, no overt embryotoxicity is associated with gestational exposure to pw ultrasound intensities of up to 30 W/cm2.