National Institute on Drug Abuse Conference report on placental proteins, drug transport, and fetal development

Influence of Prevalence of Psychoactive Substance Use in Mexican Municipalities on Early Childhood Development

Children's early development is influenced by characteristics of the child, family, and environment, including exposure to substance abuse. The aim was to examine the association of early childhood development (ECD) with the prevalence of psychoactive substance use in Mexican municipalities. We obtained ECD data from the 2015 Survey of Boys, Girls, and Women (ENIM, for its Spanish acronym), measured with the ECD Index. The prevalence of psychoactive substance use was estimated at the municipal level, using the 2016 National Survey of Drug, Alcohol, and Tobacco Use (ENCODAT, for its Spanish acronym). Multilevel logistic models were fitted to evaluate the association between drug use and inadequacies in ECD overall and in four specific ECD domains: socio-emotional, literacy-numeric, learning, and physical. Inadequate ECD was directly associated with illegal drug use (OR = 1.10; 95% CI: 1.03, 1.17). For the specific ECD domains, inadequate socio-emotional development was directly associated with illegal drug use (OR = 1.08; 95% CI: 1.01, 1.15). These findings suggest that exposure to illegal drug use may influence ECD, and especially can lead to socio-emotional problems, although this cannot be considered the unanimous determinant of the problems presented. The implementation of evidence-based interventions to prevent drug abuse is necessary.

Cocaine and its metabolites in the placenta: a systematic review of the literature

It is clear that cocaine and cocaine metabolites are present in the placenta and may harm the fetus. The results of the experimental manipulation of cocaine exposure are not reported in the literature in a consistent manner. We conducted a systematic review of selected articles that demonstrated the analytical detection of cocaine and its metabolites in the placenta and that were published from January 1, 1956-June 30, 2011 using Medline, Toxline and Scopus databases. The collected data confirm that the placenta does not act as a barrier to fetal exposure, that cocaine quickly crosses the placenta and that one of the essential roles of the placenta is to metabolize cocaine during pregnancy. Our systematic review summarized the results showing that cocaine, benzoylecgonine and norcocaine are stored in the myometrium and the placental membrane and maintain continuous drug delivery to the amniotic fluid (and to the fetus) probably via diffusion.

Illicit substance use in pregnancy - a review

Illicit substance use is not uncommon in women of childbearing age. The direct effects of illicit substance use on the mother, pregnancy and the fetus are not well understood, in contrast to the indirect effects of social disadvantage and intercurrent medical and psychiatric illness, which are well documented. We have undertaken a review of the current literature regarding the effects of illicit substance use in pregnancy and include a suggested approach to identification and management of at-risk women.

Active transport across the human placenta: impact on drug efficacy and toxicity

The human placenta expresses a large number of transport proteins. The ATP-binding cassette (ABC) family of active efflux pumps, predominantly localised to the maternal-facing syncytial membrane of placental microvilli, comprise the major placental drug efflux transporters. A variety of other transporters are also expressed in the placenta that can facilitate xenobiotic transfer in both the maternal and fetal directions. Many drugs administered in pregnancy are ABC transporter substrates, and many are either teratogenic or fetotoxic. The in vitro, in vivo and clinical evidence reviewed in this article argues that active efflux of drugs by placental transporters helps to maintain its barrier function, reducing the incidence of adverse fetal effects. ABC transporter polymorphisms may explain the wide variability observed in fetal drug concentrations, incidence of teratogenesis or drug failure in pregnancies exposed to therapeutic agents. Although our understanding of the molecular mechanics and dynamics of placental drug transfer is advancing, much work is needed to fully appreciate the significance of placental drug transporters in the face of increasing drug administration in pregnancy.

Illicit drug use and neonatal outcomes: a critical review

Although the neonatal consequences of tobacco and alcohol exposure are well established, the evidence related to prenatal illicit drug use is less consistent despite prevalent views to the contrary. The many social, psychosocial, behavioral, and biomedical risk factors for adverse birth outcomes associated with illicit drug use complicate the evaluation of neonatal effects. Placing emphasis on recent research, this review summarizes the epidemiologic literature on the neonatal impact of marijuana, opiate, and cocaine use. Of these drugs, cocaine use is most consistently related to fetal growth decrements and dose-response effects have been observed. However, studies to date have largely failed to control for associated social, psychosocial, and contextual factors. Additional recommendations for future research are provided. It is likely that interventions will need to address the factors surrounding drug use to greatly improve neonatal outcomes (e.g., social circumstances, poor nutrition, stress, infections).

The role of the endocannabinoid system in gametogenesis, implantation and early pregnancy

Maternal use of marijuana, in which the exocannabinoid Delta(9)-tetrahydrocannabinol is the most active psychoactive ingredient, is known to have adverse effects on various aspects of reproduction including ovulation, spermatogenesis, implantation and pregnancy duration. Endogenous cannabinoids of which Anandamide is the prototype are widely distributed in the body especially in the reproductive tract and pregnancy tissues and act through the same receptors as the receptor as Delta(9)-tetrahydrocannabinol. Anandamide, has been reported to have pleiotropic effects on human reproduction and in experimental animal models. It appears to be the important neuro-cytokine mediator synchronizing the embryo-endometrial development for timed implantation, the development of the embryo into the blastocyst and transport of the embryo across the fallopian tubes. The mechanisms by which it exerts these effects are unclear but could be via direct actions on the various sites within the reproductive system or its differential actions on vascular tone dependent. In this review article we bring together the current knowledge on the role of endoccanabinoids in reproduction and postulate on the potential mechanisms on how these affect reproduction. In addition, we examine its role on the endothelium and vascular smooth muscle as a potential mechanism for adverse pregnancy outcome.

Does Maternal Prenatal Stress Adversely Affect the Child’s Learning and Memory at Age Six?

Prenatal maternal stress has been shown to affect postnatal development in animals and humans. In animals, the morphology and function of the offspring's hippocampus is negatively affected by prenatal maternal stress. The present study prospectively investigated the influence of prenatal maternal stress on learning and memory of 112 children (50 boys, 62 girls, Age: M=6.7 years, SD=8.4 months), with the Test of Memory and Learning (TOMAL). Maternal stress levels were determined three times during pregnancy by self-report questionnaires. Furthermore, maternal saliva cortisol samples were used as a measure of hypothalamus-pituitary-adrenal axis functioning. Results of hierarchical multivariate regression analyses showed that maternal life events measured during the first part of pregnancy were negatively associated with the child's attention/concentration index, while controlling for overall IQ, gender, and postnatal stress. No associations were found between prenatal maternal cortisol and the offspring's learning and memory.

P-glycoprotein in the placenta: Expression, localization, regulation and function

Detailed understanding of the mechanisms employed in transfer of drugs across the placenta is essential for optimization of pharmacotherapy during pregnancy. Disclosure of drug efflux transporters as an "active component" of the placental barrier has brought new important insights into the field of transplacental pharmacokinetics. P-glycoprotein (P-gp, MDR1) is the first discovered and so far the best characterized of drug efflux transporters, whose role in the regulation of drug disposition to the fetus has been extensively studied. Expression of P-gp in the placental trophoblast layer was confirmed at the mRNA and protein levels in all phases of pregnancy, and several in vitro and in vivo studies demonstrated functional activity of the transporter in materno-fetal drug transport. P-gp is able to actively pump drugs and other xenobiotics from trophoblast cells back to the maternal circulation, providing thus protection to the fetus. This review summarizes the current knowledge on the expression, localization and function of P-gp in the placenta. In addition, we include the latest data concerning transcriptional regulation of placental P-gp expression and polymorphisms of the MDR1 gene. Clinical significance of placental P-gp and its future perspectives for pharmacotherapy during pregnancy are also discussed.

Programming effects of antenatal dexamethasone in the developing mesolimbic pathways

Elevated glucocorticoids, during pregnancy, alter emotionality and increase propensity to drug abuse later in life, albeit through substrates and mechanisms are largely unknown. In this study, we examined whether antenatal glucocorticoid exposure induces enduring structural changes in the nucleus accumbens (NAcc), an important relay point in the reward limbic circuitry. To this end, rat dams were exposed to the synthetic glucocorticoid dexamethasone (DEX) on days 18 and 19 of gestation, and stereological tools were used to assess the total volume of, and neuronal numbers in, the NAcc, as well as the density of mesencephalic dopaminergic inputs from the ventral tegmental area (VTA) to the NAcc in their adult offspring. Further, we used measures of bromodeoxyuridine incorporation into NAcc cells to examine whether DEX-induced effects on cell proliferation represent another mechanism through which glucocorticoids alter the structure of mesolimbic pathways and might influence addictive behavior. Our studies show that exposure to DEX during late gestation results in significantly reduced volumes and cell numbers in the NAcc. The latter measure correlated strongly with a reduced rate of cell proliferation in DEX-exposed animals. Moreover, the treatment resulted in a decreased number of cells expressing tyrosine hydroxylase in the VTA and an impoverished dopaminergic innervation of the NAcc. These observations, which identify glucocorticoid-sensitive structures and neurochemical targets within the developing "reward pathway," pave way for future studies designed to understand how early life events can predispose individuals for developing drug dependence in adolescent and adult life.