Prenatal Amphetamine Exposure Effects on Dopaminergic Receptors and Transporter in Postnatal Rats

Teratogen update: Amphetamines

Amphetamines are synthetic noncatecholamine sympathomimetic amines that act as psychostimulants. They have been prescribed for the treatment of attention-deficit/hyperactivity disorder (ADHD), narcolepsy, and additional health conditions. Amphetamines are also drugs of abuse. Some experimental animal studies suggested adverse developmental effects of amphetamines, including structural malformations. These effects were most often observed in experimental animals at higher dose levels than those used for treatment or abuse and at dose levels that produce maternal toxicity. Controlled studies of amphetamine use for the treatment of ADHD and other indications did not suggest that amphetamines are likely to cause structural malformations, although there are three studies associating medication for ADHD or methamphetamine abuse with gastroschisis. We did not locate studies on the neurobehavioral effects of prenatal exposures to therapeutic amphetamine use. Amphetamine abuse was associated with offspring neurobehavioral abnormalities, but lack of adequate adjustment for confounding interferes with interpretation of the associations. Adverse effects of methamphetamine abuse during pregnancy may be due to factors associated with drug abuse rather than methamphetamine itself. The adverse effects observed in methamphetamine abuse studies may not be extrapolatable to amphetamine medication use.

Mapping of the prenatal and postnatal methamphetamine effects on D1-like dopamine, M1 and M2 muscarinic receptors in rat central nervous system

Methamphetamine (MA) is worldwide known drug with high potential for addiction that causes dopamine, noradrenaline and serotonin release. MA is also able to increase acetylcholine levels in adult rodents. The aim of this study was to map changes in D₁-like dopamine receptors (DR), M₁ and M₂ muscarinic receptors (MR), and the total number of MR (M₁-M₅ MR) in the CNS of rats exposed to MA prenatally and in adulthood. Rat mothers were exposed to MA (5mg/kg s.c.) or saline during the entire gestation period and their male offspring were administered in adulthood with single MA (1mg/kg) or saline injection. Thus, the animals were divided into 4 groups: prenatally MA-exposed rats treated with saline (MA/S) or MA (MA/MA) in adulthood and prenatally saline-exposed rats treated with saline (S/S) or MA (S/MA) in adulthood. One hour after the acute treatment animals were sacrificed and their brains were removed. The numbers of M₁, M₂, total MR, and D₁-DR were measured by autoradiography. The main effect was detected in the hippocampus with the most affected M₁ MR. D₁-DR were decreased in motor cortex and substantia nigra. M₁MR were decreased in caudate-putamen, dorsal hippocampus, CA1, CA3 and dentate gyrus (DG). M₂MR were decreased in DG only. Total number of MR was moreover decreased in dorsal hippocampus, CA1, CA3 and DG. Our results have shown different patterns of changes in DR and MR, suggesting a pilot role of M₁ MR in the CNS changes induced by prenatal and adult MA exposure.

Prenatal Alcohol Exposure in Rodents As a Promising Model for the Study of ADHD Molecular Basis

A physiological parallelism, or even a causal effect relationship, can be deducted from the analysis of the main characteristics of the “Alcohol Related Neurodevelopmental Disorders” (ARND), derived from prenatal alcohol exposure (PAE), and the behavioral performance in the Attention-deficit/hyperactivity disorder (ADHD). These two clinically distinct disease entities, exhibits many common features. They affect neurological shared pathways, and also related neurotransmitter systems. We briefly review here these parallelisms, with their common and uncommon characteristics, and with an emphasis in the subjacent molecular mechanisms of the behavioral manifestations, that lead us to propose that PAE in rats can be considered as a suitable model for the study of ADHD.

The effects of amphetamine exposure on juvenile rats on the neuronal morphology of the limbic system at prepubertal, pubertal and postpubertal ages

Amphetamines (AMPH) are psychostimulants widely used for therapy as well as for recreational purposes. Previous results of our group showed that AMPH exposure in pregnant rats induces physiological and behavioral changes in the offspring at prepubertal and postpubertal ages. In addition, several reports have shown that AMPH are capable of modifying the morphology of neurons in some regions of the limbic system. These modifications can cause some psychiatric conditions. However, it is still unclear if there are changes to behavioral and morphological levels when low doses of AMPH are administered at a juvenile age. The aim of this study was to assess the effect of AMPH administration (1mg/kg) in Sprague-Dawley rats (postnatal day, PD21-PD35) on locomotor activity in a novel environment and compare the neuronal morphology of limbic system areas at three different ages: prepubertal (PD 36), pubertal (PD50) and postpubertal (PD 62). We found that AMPH altered locomotor activity in the prepubertal group, but did not have an effect on the other two age groups. The Golgi-Cox staining method was used to describe the neural morphology of five limbic regions: (Layers 3 and 5) the medial prefrontal cortex (mPFC), the dorsal and ventral hippocampus, the nucleus accumbens and the amygdala, showing that AMPH induced changes at pubertal ages in arborization and spine density of these neurons, but interestingly these changes did not persist at postpubertal ages. Our findings suggest that even early-life AMPH exposure does not induce long-term behavioral and morphological changes, however it causes alterations at pubertal ages in the limbic system networks, a stage of life strongly associated with the development of substance abuse behaviors.

Developmental consequences of fetal exposure to drugs: what we know and what we still must learn

Most drugs of abuse easily cross the placenta and can affect fetal brain development. In utero exposures to drugs thus can have long-lasting implications for brain structure and function. These effects on the developing nervous system, before homeostatic regulatory mechanisms are properly calibrated, often differ from their effects on mature systems. In this review, we describe current knowledge on how alcohol, nicotine, cocaine, amphetamine, Ecstasy, and opiates (among other drugs) produce alterations in neurodevelopmental trajectory. We focus both on animal models and available clinical and imaging data from cross-sectional and longitudinal human studies. Early studies of fetal exposures focused on classic teratological methods that are insufficient for revealing more subtle effects that are nevertheless very behaviorally relevant. Modern mechanistic approaches have informed us greatly as to how to potentially ameliorate the induced deficits in brain formation and function, but conclude that better delineation of sensitive periods, dose-response relationships, and long-term longitudinal studies assessing future risk of offspring to exhibit learning disabilities, mental health disorders, and limited neural adaptations are crucial to limit the societal impact of these exposures.