Cocaine exposure prebreeding to weaning: maternal and offspring effects

Cocaine-induced neurodevelopmental deficits and underlying mechanisms

Exposure to drugs early in life has complex and long-lasting implications for brain structure and function. This review summarizes work to date on the immediate and long-term effects of prenatal exposure to cocaine. In utero cocaine exposure produces disruptions in brain monoamines, particularly dopamine, during sensitive periods of brain development, and leads to permanent changes in specific brain circuits, molecules, and behavior. Here, we integrate clinical studies and significance with mechanistic preclinical studies, to define our current knowledge base and identify gaps for future investigation. Birth Defects Research (Part C) 108:147-173, 2016. © 2016 Wiley Periodicals, Inc.

Effects of cocaine on maternal behavior and neurochemistry

Drug addiction is a chronic relapsing disorder that involves drug seeking and abuse despite the negative social and health consequences. While the potential effects of cocaine on child development have been extensively studied over the last 30 years, few researchers have focused on the effects of cocaine on maternal behavior, which includes offspring care and maternal aggression towards an unfamiliar individual. In humans, maternal cocaine use can lead to child neglect, abuse, and disrupt the mother-child bond. While it has been argued the developmental effects of maternal cocaine use on children were initially overstated, it is clear that disruptions of typical maternal behavior (i.e. postpartum depression, anxiety disorders) are detrimental to the physical and emotional health of offspring. Cocaine use in mothers is commonly associated with psychological disorders, including depression and anxiety, and it is postulated that many of the negative effects of maternal cocaine use on offspring are mediated through changes in maternal behavior. This review will summarize research on cocaine and maternal behavior in animal and human studies, discuss potential mechanisms, and suggest therapeutic strategies for treating cocaine-affected maternal behavior which may improve the physical and behavioral health of both mother and child. The primary objective is to stimulate future communication, cooperation, and collaboration between researchers who use animals and humans to study cocaine and maternal behavior.

Social behavior of offspring following prenatal cocaine exposure in rodents: a comparison with prenatal alcohol

Clinical and experimental reports suggest that prenatal cocaine exposure (PCE) alters the offsprings' social interactions with caregivers and conspecifics. Children exposed to prenatal cocaine show deficits in caregiver attachment and play behavior. In animal models, a developmental pattern of effects that range from deficits in play and social interaction during adolescence, to aggressive reactions during competition in adulthood is seen. This review will focus primarily on the effects of PCE on social behaviors involving conspecifics in animal models. Social relationships are critical to the developing organism; maternally directed interactions are necessary for initial survival. Juvenile rats deprived of play behavior, one of the earliest forms of non-mother directed social behaviors in rodents, show deficits in learning tasks and sexual competence. Social behavior is inherently complex. Because the emergence of appropriate social skills involves the interplay between various conceptual and biological facets of behavior and social information, it may be a particularly sensitive measure of prenatal insult. The social behavior surveyed include social interactions, play behavior/fighting, scent marking, and aggressive behavior in the offspring, as well as aspects of maternal behavior. The goal is to determine if there is a consensus of results in the literature with respect to PCE and social behaviors, and to discuss discrepant findings in terms of exposure models, the paradigms, and dependent variables, as well as housing conditions, and the sex and age of the offspring at testing. As there is increasing evidence that deficits in social behavior may be sequelae of developmental exposure alcohol, we compare changes in social behaviors reported for prenatal alcohol with those reported for prenatal cocaine. Shortcomings in the both literatures are identified and addressed in an effort to improve the translational value of future experimentation.

The medial preoptic area is necessary for motivated choice of pup- over cocaine-associated environments by early postpartum rats

Converging evidence suggests that the motivation to seek cocaine during the postpartum period is significantly impacted by the competing incentives of offspring, a stimulus unique to this life stage. In the present study, the functional role of the medial preoptic area (mPOA), a critical site involved in maternal responsiveness, on processing incentive value of pup-associated cues and influencing response allocation for pup- over cocaine-associated environments was investigated using a concurrent pup/cocaine choice conditioned place preference (CPP) paradigm. Early postpartum females with bilateral guide cannulae aimed into the mPOA or into anatomical control sites were conditioned, from postpartum days (PPD) 4 to 7, to associate different uniquely featured environments with pups or cocaine. CPP was tested on PPD8 following intra-mPOA infusions of either 2% bupivacaine or saline vehicle. In two additional experiments, the effects of intra-mPOA infusions of bupivacaine on expression of conditioned responding induced by environments associated with either pups or cocaine were examined separately. Transient inactivation of the mPOA selectively blocked the conditioned preferences for pup-associated environments, significantly contrasting the robust pup-CPP found in non-surgical and intra-mPOA vehicle-treated females. In contrast, mPOA inactivation failed to alter cocaine-CPP in postpartum females. When given a choice between environments associated with pups or cocaine, transient functional inactivation of the mPOA altered choice behavior, biasing the preference of females toward cocaine-associated environments, such that almost all preferred cocaine- and none the pup-associated option. The anatomical specificity was revealed when inactivation of adjacent regions to the mPOA did not affect CPP responses for pups. The findings support a critical role for the mPOA in mediating pup-seeking behavior, and further suggest that the competing properties of pups over alternative incentives, including drugs of abuse, rely on mPOA integrity to provide relevant pup-related information to the circuitry underlying the choice behavior between pups and alternative stimuli.

Cocaine addiction in mothers: potential effects on maternal care and infant development

Maternal cocaine addiction is a significant public health issue particularly affecting children, with high rates of reported abuse, neglect, and foster care placement. This review examines both preclinical and clinical evidence for how cocaine abuse may affect maternal care and infant development, exploring brain, behavioral, and neuroendocrine mechanisms. There is evidence that cocaine affects infant development both directly, via in utero exposure, and indirectly via alterations in maternal care. Two neural systems known to play an important role in both maternal care and cocaine addiction are the oxytocin and dopamine systems, mediating social and reward-related behaviors and stress reactivity. These same neural mechanisms may also be involved in the infant's development of vulnerability to addiction. Understanding the neuroendocrine pathways involved in maternal behavior and addiction may help facilitate earlier, more effective interventions to help substance-abusing mothers provide adequate care for their infant and perhaps prevent the intergenerational transmission of risk.

Effect of methamphetamine exposure during prenatal and preweaning periods lasts for generations in rats

Our previous studies demonstrated that methamphetamine (MA) administration during gestation and/or lactation affects maternal behavior in rats and that birth weight and sensory-motor coordination of their pups are also influenced. The present study tested the hypothesis that the effect of MA induces long-term changes affecting second generation of rats that were not exposed to the drug. Adult females exposed during prenatal and preweaning periods to 5 mg/kg MA daily, were examined for regularity of estrous cycle and mated with stimulus, unexposed males. Dams (nontreated absolute control, saline- and MA-exposed) were observed with their pups in two tests of maternal behavior (observational and retrieval tests). Their pups were further tested throughout the preweaning period to examine their development. Our data demonstrate that MA-exposed mothers displayed more nursing, were more often in the nest and in contact with their pups, and were faster in retrieving their pups than saline-exposed and/or control mothers. There were no differences in litter characteristics, birth weight and weight gain of pups between groups. Interestingly, pups from mothers exposed to MA during prenatal and preweaning period had impaired sensory-motor coordination. They achieved righting reflex in mid-air later than both control groups. Additionally, they had more falls in rotarod and bar-holding tests than pups from both control and saline-exposed mothers. In homing performance, pups from MA- and saline-exposed dams learned slower to return to the home box than pups from control dams. Thus, the present study demonstrates that MA abused by mothers may affect two generations of their offspring.

Cocaine disrupts pup-induced maternal behavior in juvenile and adult rats

Impaired onset of maternal behavior in first generation rat dams was previously correlated with rearing by cocaine-treated dams and prenatal cocaine exposure. Pup-induced maternal behavior in non-lactating rats has not been examined with regard to cocaine exposure and rearing conditions. First generation male and female juveniles and young adult males reared by cocaine-treated or control dams and prenatally exposed to either cocaine or control conditions were tested for pup-induced maternal behavior at postnatal days 28 and 60. We now report disruptions in pup-induced maternal behavior in both 28 and 60 day old first generation offspring attributable to rearing condition and prenatal cocaine exposure.

Cocaine treatment and prenatal environment interact to disrupt intergenerational maternal behavior in rats

The link between impaired maternal behavior (MB) and cocaine treatment could result from drug-induced decreases in maternal reactivity to offspring, prenatal drug exposure (PDE) in offspring that could alter their ability to elicit MB, or the interaction of both, which could subsequently impair MB of the 1st-generation dams. Following chronic or intermittent cocaine or saline treatment during gestation, rat dams rearing natural or cross-fostered litters were compared along with untreated dams for MB. Untreated 1st-generation females with differentially treated rearing dams and PDE were tested for MB with their natural litters. The authors report disruptions in MB in dams and their 1st-generation offspring, attributable to main and interaction effects of maternal treatment, litter PDE, and rearing experience.

Methamphetamine administration during gestation impairs maternal behavior

Previous studies demonstrated that repeated drug exposure, such as opiates or cocaine, during the gestation period attenuates maternal behavior of rats; however, it is not known whether methamphetamine (MA), a drug whose usage has increased recently, negatively affects maternal behavior as well. Therefore, the present study tested the hypothesis that repeated subcutaneous administration of MA (5 mg/kg daily) throughout the entire gestation period alters maternal behavior. Dams (control, saline-, and MA-treated) were observed with their pups in two types of tests. In the observation test, 11 types of activities and three types of nursing positions of mothers were recorded 10 times during each 50-min session for the 22-day lactation period. A decrease in nursing and active maternal behavior was found in MA-treated mothers relative to control rats. In addition, stereotypic behavior such as rearing and sniffing was increased in MA- as well as in saline-treated mothers relative to controls. All mothers, regardless of the treatment, displayed significantly less maternal behavior and more nonmaternal activities as postpartum time progressed. In the retrieval test, mothers also were tested for pup retrieval from postpartum Days 1 through 12. MA-treated mothers were slower in retrieving the first pup, returning the first pup into the nest, and returning all pups into the nest relative to controls or saline-treated mothers. Interestingly, the latency to return all pups to the nest was longer in saline-treated mothers relative to controls. In conclusion, the present study demonstrates a novel finding that MA administered during the gestation period has a negative effect on maternal behavior.

Maternal behavior is impaired by methamphetamine administered during pre-mating, gestation and lactation

Previous studies demonstrated that stimulant drugs, such as cocaine or amphetamine, administered during gestation or lactation may attenuate maternal behavior in rats. The effect of methamphetamine (MA), a drug whose usage has increased lately, on maternal behavior has not yet been investigated. The present study tested the effect of MA (5 mg/kg daily) administered prior to, during and after gestation on maternal behavior. Regularity of the estrous cycle, the incidence of impregnation, and the weight gain was compared between groups (control, saline- and MA-treated). Maternal behavior was examined using two tests: Observation test (without disturbance of the mother and pups) and Retrieval test (with short separation of pups from the mother). All tests were conducted prior to dosing each day. In the Observation test, MA decreased the blanket position of active nursing, while increasing passive nursing. There were no MA-induced changes in other maternal activities such as mother being in the nest, in contact with pups, or grooming pups. MA increased some non-maternal activities, such as drinking, eating, and sleeping, while decreasing stereotypic behavior (sniffing and rearing) when compared to controls. In the Retrieval test, MA-treated mothers were slower in retrieving the first pup, returning the first pup into the nest, and returning all pups into the nest. Interestingly, there were differences in maternal behavior also in saline-treated mothers relative to controls. Saline-treated mothers spent more time in the nest and groomed pups more than controls or MA-treated mothers. In conclusion, the present study demonstrates a novel finding that MA administered during pre-mating, gestational and lactational periods has a negative effect on maternal behavior toward pups.

Fetal effects of cocaine: an updated meta-analysis

BACKGROUND

A very large number of women in the reproductive age group consume cocaine, leading to grave concerns regarding the long term health of millions of children after in utero exposure. The results of controlled studies have been contradictory, leading to confusion, and, possible, misinformation and misperception of teratogenic risk.

OBJECTIVE

To systematically review available data on pregnancy outcome when the mother consumed cocaine.

METHODS

A meta-analysis of all epidemiologic studies based on a priori criteria was conducted. Comparisons of adverse events in subgroups of exposed vs. unexposed children were performed. Analyses were based on several exposure groups: mainly cocaine, cocaine plus polydrug, polydrug but no cocaine, and drug free.

RESULTS

Thirty three studies met our inclusion criteria. For all end points of interest (rates of major malformations, low birth weight, prematurity, placental abruption, premature rupture of membrane [PROM], and mean birth weight, length and head circumference), cocaine-exposed infants had higher risks than children of women not exposed to any drug. However, most of these adverse effects were nullified when cocaine exposed children were compared to children exposed to polydrug but no cocaine. Only the risk of placental abruption and premature rupture of membranes were statistically associated with cocaine use itself.

CONCLUSIONS

Many of the perinatal adverse effects commonly attributed to cocaine may be caused by the multiple confounders that can occur in a cocaine using mother. Only the risk for placental abruption and PROM could be statistically related to cocaine. For other adverse effects, additional studies will be needed to ensure adequate statistical power.

Dose-dependent effects of multiple acute cocaine injections on maternal behavior and aggression in Sprague-Dawley rats

Rat dams, which had no prior drug treatment, were either nontreated controls or were injected subcutaneously 4 times during a 10-day period with a single dose of 30, 15 or 7.5 mg/kg of cocaine hydrochloride HCl, or normal saline. Injections were given immediately postpartum following delivery of their final pup (PPD 1), and again on postpartum day 3 (PPD 3), postpartum day 6 (PPD 6) and postpartum day 10 (PPD 10). Dams were observed 30 min following injections for maternal behavior (MB) towards 8 surrogate male pups on PPD 1 and PPD 3 and for aggression towards a male or female intruder in the presence of their litter on PPD 6 and PPD 10. Compared to saline and untreated controls, cocaine-treated dams exhibited more disruptions in MB on both PPD 1 and PPD 3 and were less aggressive towards an intruder, regardless of intruder sex, on PPD 6 and PPD 10. In most cases MB was altered in a dose-dependent manner with the higher doses of cocaine resulting in a greater disruption of behavior.

Differential effects of prenatal cocaine and retinoic acid on activity level throughout day and night

Prenatal cocaine exposure is associated with disrupted state control and lowered activity levels. Prenatal retinoic acid excess also influences activity levels in laboratory rats. Activity level is usually monitored during a brief period in young offspring. The effects of these drugs on pup activity levels throughout the day is unknown. There is also little information on the long-lasting effects of these teratogens in adult animals. We compared the daily activity of rats which were prenatally exposed to cocaine or retinoic acid (RA). Appropriate control groups were also used. The offspring were evaluated for activity levels in a neophobic situation and for a 22-h period in same-sex groups of 3 littermates. As both pups and adults, the cocaine groups were hypoactive while the RA group was hyperactive when first placed into the testing cage (neophobic situation). Similarly, during the remainder of the 22-h testing period, the pup and adult cocaine animals exhibited reduced activity levels while the RA animals exhibited elevated activity levels. Thus, prenatal cocaine and retinoic acid exposures affected offspring activity levels differently, both drugs have long-lasting neurobehavioral effects that persist into adulthood, and effects are influenced by time-of-day. Strain-dependent differences and mechanisms of action are discussed.

Perinatal cocaine reduces responsiveness to cocaine and causes alterations in exploratory behavior and visual discrimination in young-adult rats

Lister hooded female rats were exposed to either saline or cocaine (20 mg/kg s.c.) from gestational day 10 every other day until weaning (postnatal day 25). The effects of maternal cocaine exposure on novelty-induced exploration and on spontaneous and cocaine-induced motor activity were evaluated in young-adult male offspring (4 weeks after weaning). Rats exposed to cocaine during development spent less time exploring two novel objects. Lack of habituation upon the second presentation of the objects and failure in the ability to discriminate between the novel and familiar object were also found in cocaine exposed offspring. Moreover, maternal cocaine treatment did not affect spontaneous motor activity (active time, average speed and rearing) in rats subjected to an open field test. Furthermore, perinatal exposure to cocaine significantly attenuated acute cocaine (15 mg/kg i.p.)-induced hyperactivity. These data indicate that developmental exposure to cocaine, at dose levels below those producing gross malformations and/or overt signs of neurotoxicity, causes behavioral changes characterized by an altered responsiveness to environmental and pharmacological challenges.

Prenatal cocaine but not prenatal malnutrition affects foster mother-pup interactions in rats

The separate and combined effects of prenatal cocaine exposure and malnutrition on mother-pup interactions in rats were assessed daily from postnatal day 2 to day 21. Sprague-Dawley dams were fed a diet of low protein content (6% casein), an isocaloric diet of adequate protein content (25% casein, control), or a laboratory chow diet prior to mating and throughout pregnancy. Within each diet group, rats received either cocaine injections (30 mg/kg IP two times per week prior to mating and then 30 mg/kg SC daily from days 3 to 18 of pregnancy) or saline injections. Litters were fostered on the day of birth to control mothers (i.e., nondrug-exposed dams fed the control or chow diet). Foster mothers fed the 25% casein diet showed increased contact with cocaine-exposed pups compared with nondrug-exposed pups in the second postnatal week but lower levels as the pups approached weaning. Passive nursing was increased in dams caring for prenatally malnourished, cocaine-exposed pups compared with those caring for similar pups with no drug exposure. Chow-fed mothers did not differ in their behavior towards pups with or without prenatal cocaine treatment. Prenatal cocaine and malnutrition independently compromised birth weight and various reflexive milestones but the attainment of physical milestones was affected only by prenatal cocaine. There were no additive effects of the two prenatal insults on any measure of mother-pup interaction or pup development.

The effects of cocaine exposure prior to and during pregnancy in rats fed low or adequate protein diets

Sprague-Dawley rats were fed a diet of low protein content (6% casein), an isocaloric diet of adequate protein content (25% casein), or a laboratory chow diet for 5 weeks prior to mating and throughout pregnancy. Within each diet group, rats received either cocaine (30 mg/kg IP two times per week prior to mating and 30 mg/kg or 40 mg/kg SC daily from days 3 to 18 of pregnancy) or saline injections. Cocaine produced a greater reduction in food intake during pregnancy in the malnourished group compared with the other two diet groups. The effect of cocaine on food intake was minimal in chow-fed rats. Weight gain in pregnancy was reduced by cocaine in a dose-dependent manner, and by malnutrition. Both prenatal cocaine and malnutrition impaired skeletal maturation of the pups, but there was no additive effect of the two insults on this measure. Litter size was significantly reduced by the 40 mg/kg, but not by the 30 mg/kg dose of cocaine across all diet groups. Consequently, the 40 mg/kg dose of cocaine proved to be fetotoxic in this model. Birth weight was significantly reduced by prenatal malnutrition but not by prenatal cocaine. Gestation length was unaffected by either insult. Hence, the ability to detect a diet x drug interaction was dependent upon the variable being measured.