Long-term consequences of prenatal exposure to cocaine or related drugs: effects on rat brain monoaminergic receptors

Transcriptomic effects of paternal cocaine-seeking on the reward circuitry of male offspring

It has been previously established that paternal development of a strong incentive motivation for cocaine can predispose offspring to develop high cocaine-seeking behavior, as opposed to sole exposure to the drug that results in drug resistance in offspring. However, the adaptive changes of the reward circuitry have not been fully elucidated. To infer the key nuclei and possible hub genes that determine susceptibility to addiction in offspring, rats were randomly assigned to three groups, cocaine self-administration (CSA), yoked administration (Yoke), and saline self-administration (SSA), and used to generate F1. We conducted a comprehensive transcriptomic analysis of the male F1 offspring across seven relevant brain regions, both under drug-naïve conditions and after cocaine self-administration. Pairwise differentially expressed gene analysis revealed that the orbitofrontal cortex (OFC) exhibited more pronounced transcriptomic changes in response to cocaine exposure, while the dorsal hippocampus (dHip), dorsal striatum (dStr), and ventral tegmental area (VTA) exhibited changes that were more closely associated with the paternal voluntary cocaine-seeking behavior. Consistently, these nuclei showed decreased dopamine levels, elevated neuronal activation, and elevated between-nuclei correlations, indicating dopamine-centered rewiring of the midbrain circuit in the CSA offspring. To determine if possible regulatory cascades exist that drive the expression changes, we constructed co-expression networks induced by paternal drug addiction and identified three key clusters, primarily driven by transcriptional factors such as MYT1L, POU3F4, and NEUROD6, leading to changes of genes regulating axonogenesis, synapse organization, and membrane potential, respectively. Collectively, our data highlight vulnerable neurocircuitry and novel regulatory candidates with therapeutic potential for disrupting the transgenerational inheritance of vulnerability to cocaine addiction.

Paternal methamphetamine exposure induces higher sensitivity to methamphetamine in male offspring through driving ADRB1 on CaMKII-positive neurons in mPFC

Paternal abuse of drugs, such as methamphetamine (METH), elevates the risk of developing addiction in subsequent generations, however, its underlying molecular mechanism remains poorly understood. Male adult mice (F0) were exposed to METH for 30 days, followed by mating with naïve female mice to create the first-generation mice (F1). When growing to adulthood, F1 were subjected to conditioned place preference (CPP) test. Subthreshold dose of METH (sd-METH), insufficient to induce CPP normally, were used in F1. Selective antagonist (betaxolol) for β1-adrenergic receptor (ADRB1) or its knocking-down virus were administrated into mPFC to regulate ADRB1 function and expression on CaMKII-positive neurons. METH-sired male F1 acquired sd-METH-induced CPP, indicating that paternal METH exposure induce higher sensitivity to METH in male F1. Compared with saline (SAL)-sired male F1, CaMKII-positive neuronal activity was normal without sd-METH, but strongly evoked after sd-METH treatment in METH-sired male F1 during adulthood. METH-sired male F1 had higher ADRB1 levels without sd-METH, which was kept at higher levels after sd-METH treatment in mPFC. Either inhibiting ADRB1 function with betaxolol, or knocking-down ADRB1 level on CaMKII-positive neurons (ADRB1CaMKII) with virus transfection efficiently suppressed sd-METH -evoked mPFC activation, and ultimately blocked sd-METH-induced CPP in METH-sired male F1. In the process, the p-ERK1/2 and ΔFosB may be potential subsequent signals of mPFC ADRB1CaMKII. The mPFC ADRB1CaMKII mediates paternal METH exposure-induced higher sensitivity to drug addiction in male offspring, raising a promising pharmacological target for predicting or treating transgenerational addiction.

The Ontogenesis of Mammalian Sleep: Form and Function

PURPOSE OF REVIEW

To present an up-to-date review and synthesis of findings about perinatal sleep development and function. I discuss landmark events in sleep ontogenesis, evidence that sleep promotes brain development and plasticity, and experimental considerations in this topic.

RECENT FINDINGS

Mammalian sleep undergoes dramatic changes in expression and regulation during perinatal development. This includes a progressive decrease in rapid-eye-movement (REM) sleep time, corresponding increases in nonREM sleep and wake time, and the appearance of mature sleep regulatory processes (homeostatic and circadian). These developmental events coincide with periods of rapid brain maturation and heightened synaptic plasticity. The latter involve an initial experience-independent phase, when circuit development is guided by spontaneous activity, and later occurring critical periods, when these circuits are shaped by experience.

SUMMARY

These ontogenetic changes suggest important interactions between sleep and brain development. More specifically, sleep may promote developmental programs of synaptogenesis and synaptic pruning and influence the opening and closing of critical periods of brain plasticity.

Prenatal cocaine exposure and its impact on cognitive functions of offspring: a pathophysiological insight

It is estimated that approximately 0.5%-3% of fetuses are prenatally exposed to cocaine (COC). The neurodevelopmental implications of this exposure are numerous and include motor skill impairments, alterations of social function, predisposition to anxiety, and memory function and attention deficits; these implications are commonly observed in experimental studies and ultimately affect both learning and IQ. According to previous studies, the clinical manifestations of prenatal COC exposure seem to persist at least until adolescence. The pathophysiological cellular processes that underlie these impairments include dysfunctional myelination, disrupted dendritic architecture, and synaptic alterations. On a molecular level, various neurotransmitters such as serotonin, dopamine, catecholamines, and γ-aminobutyric acid seem to participate in this process. Finally, prenatal COC abuse has been also associated with functional changes in the hormones of the hypothalamic-pituitary-adrenal axis that mediate neuroendocrine responses. The purpose of this review is to summarize the neurodevelopmental consequences of prenatal COC abuse, to describe the pathophysiological pathways that underlie these consequences, and to provide implications for future research in the field.

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.

Prenatal antidepressant exposure: clinical and preclinical findings

Pharmacological treatment of any maternal illness during pregnancy warrants consideration of the consequences of the illness and/or medication for both the mother and unborn child. In the case of major depressive disorder, which affects up to 10-20% of pregnant women, the deleterious effects of untreated depression on the offspring can be profound and long lasting. Progress has been made in our understanding of the mechanism(s) of action of antidepressants, fetal exposure to these medications, and serotonin's role in development. New technologies and careful study designs have enabled the accurate sampling of maternal serum, breast milk, umbilical cord serum, and infant serum psychotropic medication concentrations to characterize the magnitude of placental transfer and exposure through human breast milk. Despite this progress, the extant clinical literature is largely composed of case series, population-based patient registry data that are reliant on nonobjective means and retrospective recall to determine both medication and maternal depression exposure, and limited inclusion of suitable control groups for maternal depression. Conclusions drawn from such studies often fail to incorporate embryology/neurotransmitter ontogeny, appropriate gestational windows, or a critical discussion of statistically versus clinically significant. Similarly, preclinical studies have predominantly relied on dosing models, leading to exposures that may not be clinically relevant. The elucidation of a defined teratological effect or mechanism, if any, has yet to be conclusively demonstrated. The extant literature indicates that, in many cases, the benefits of antidepressant use during pregnancy for a depressed pregnant woman may outweigh potential risks.

Drugs in pregnancy: the effects on mother and her progeny

Drug abuse during pregnancy is a growing problem in all developed countries all over the world. The drugs easily cross the placental barrier into the fetal body and are present also in the maternal milk. Therefore, it may affect the development of the child pre- as well as postnatally. The effects of prenatal drug exposure are long-lasting and persist until adulthood. The present review summarizes the clinical and experimental evidence showing how opioids and psychostimulants can affect maternal behavior of drug-abusing mother and the development of their offspring.

Sleep and developmental plasticity not just for kids

In a variety of mammalian species, sleep amounts are highest during developmental periods of rapid brain development and synaptic plasticity than at any other time in life [Frank, M. G. & Heller, H. C. (1997a). Development of REM and slow wave sleep in the rat. American Journal of Physiology, 272, R1792-R1799; Jouvet-Mounier, D., Astic, L., & Lacote, D. (1970). Ontogenesis of the states of sleep in rat, cat and guinea pig during the first postnatal month. Developmental Psychobiology, 2, 216-239; Roffwarg, H. P., Muzio, J. N., & Dement, W. C. (1966). Ontogenetic development of the human sleep-dream cycle. Science, 604-619]. Many of the mechanisms governing developmental plasticity also mediate plasticity in the adult brain. Therefore, studying the role of sleep in developmental plasticity may provide insights more generally into sleep function across the lifespan. In this chapter, I review the evidence that supports a critical role for sleep in developmental brain plasticity. I begin with an overview of past studies that support a role for sleep in general brain maturation. This is followed by more recent findings in the developing visual cortex that more specifically address a possible role for sleep in cortical plasticity.

Prenatal Cocaine Disrupts Serotonin Signaling-Dependent Behaviors: Implications for Sex Differences, Early Stress and Prenatal SSRI Exposure

Prenatal cocaine (PC) exposure negatively impacts the developing nervous system, including numerous changes in serotonergic signaling. Cocaine, a competitive antagonist of the serotonin transporter, similar to selective serotonin reuptake inhibitors (SSRIs), also blocks dopamine and norepinephrine transporters, leaving the direct mechanism through which cocaine disrupts the developing serotonin system unclear. In order to understand the role of the serotonin transporter in cocaine's effect on the serotonergic system, we compare reports concerning PC and prenatal antidepressant exposure and conclude that PC exposure affects many facets of serotonergic signaling (serotonin levels, receptors, transporters) and that these effects differ significantly from what is observed following prenatal SSRI exposure. Alterations in serotonergic signaling are dependent on timing of exposure, test regimens, and sex. Following PC exposure, behavioral disturbances are observed in attention, emotional behavior and stress response, aggression, social behavior, communication, and like changes in serotonergic signaling, these effects depend on sex, age and developmental exposure. Vulnerability to the effects of PC exposure can be mediated by several factors, including allelic variance in serotonergic signaling genes, being male (although fewer studies have investigated female offspring), and experiencing the adverse early environments that are commonly coincident with maternal drug use. Early environmental stress results in disruptions in serotonergic signaling analogous to those observed with PC exposure and these may interact to produce greater behavioral effects observed in children of drug-abusing mothers. We conclude that based on past evidence, future studies should put a greater emphasis on including females and monitoring environmental factors when studying the impact of PC exposure.

Methylxanthines during pregnancy and early postnatal life

World-wide, many fetuses and infants are exposed to methylxanthines via maternal consumption of coffee and other beverages containing these substances. Methylxanthines (caffeine, theophylline and aminophylline) are also commonly used as a medication for apnea of prematurity.The metabolism of methylxanthines is impaired in pregnant women, fetuses and neonates, leading to accumulating levels thereof. Methylxanthines readily passes the placenta barrier and enters all tissues and thus may affect the fetus/newborn at any time during pregnancy or postnatal life, given that the effector systems are mature.At clinically relevant doses, the major effector system for methylxanthines is adenosine receptors. Animal studies suggest that adenosine receptors in the cardiovascular, respiratory and immune system are developed at birth, but that cerebral adenosine receptors are not fully functional. Furthermore animal studies have shown protective positive effects of methylxanthines in situations of hypoxia/ischemia in neonates. Similarly, a positive long-term effect on lung function and CNS development was found in human preterm infants treated with high doses of caffeine for apneas. There is now evidence that the overall benefits from methylxanthine therapy for apnea of prematurity outweigh potential short-term risks.On the other hand it is important to note that experimental studies have indicated that long-term effects of caffeine during pregnancy and postnatally may include altered behavior and altered respiratory control in the offspring, although there is currently no human data to support this.Some epidemiology studies have reported negative effects on pregnancy and perinatal outcomes related to maternal ingestion of high doses of caffeine, but the results are inconclusive. The evidence base for adverse effects of caffeine in first third of pregnancy are stronger than for later parts of pregnancy and there is currently insufficient evidence to advise women to restrict caffeine intake after the first trimester.

Postnatal manganese exposure alters the expression of D2L and D2S receptor isoforms: relationship to PKA activity and Akt levels

Postnatal manganese chloride (Mn) exposure causes persistent changes in presynaptic dopamine (DA) functioning (e.g., Mn reduces DA transporter levels and DA uptake), but evidence that Mn affects postsynaptic DA receptors and their associated second messenger systems is equivocal. Therefore, a goal of the present study was to determine whether exposing rats to Mn on postnatal days (PD) 1-21 would cause long-term alterations in D2 long (D2L) and D2 short (D2S) receptors that were detectible in adulthood (i.e., on PD 90). Signaling systems associated with D2 receptors were also assessed. Specifically, we measured protein kinase A (PKA) activity in the dorsal striatum and prefrontal cortex (PFC), whereas immunoblotting was used to quantify phosphorylated Akt (p-Akt) and phosphorylated ERK. Results showed that early Mn exposure caused a persistent elevation of D2L and D2S protein expression in the dorsal striatum, as well as an increase in the number of D2 binding sites. Conversely, Mn reduced D2 specific binding in the PFC on PD 90. PKA activity of Mn-treated rats was enhanced in both the dorsal striatum and PFC, whereas p-Akt levels were elevated in the dorsal striatum. When considered together, these results suggest that postnatal Mn exposure either directly or indirectly alters the functioning of postsynaptic DA receptors. One possibility is that early Mn exposure depresses presynaptic dopaminergic functioning and reduces DA levels, thereby causing an up-regulation of D2 receptors and a dysregulation of DA-associated signaling pathways. An alternative explanation is that early Mn exposure affects D2 receptors and PKA/p-Akt levels via independent mechanisms.

Prenatal cocaine exposure increases anxiety, impairs cognitive function and increases dendritic spine density in adult rats: influence of sex

Cocaine exposure during pregnancy can impact brain development and have long-term behavioral consequences. The present study examined the lasting consequences of prenatal cocaine (PN-COC) exposure on the performance of cognitive tasks and dendritic spine density in adult male and female rats. From gestational day 8 to 20, dams were treated daily with 30 mg/kg (ip) of cocaine HCl or saline. At 62 days of age, offspring were tested consecutively for anxiety, locomotion, visual memory and spatial memory. PN-COC exposure significantly increased anxiety in both sexes. Object recognition (OR) and placement (OP) tasks were used to assess cognitive function. Behavioral tests consisted of an exploration trial (T1) and a recognition trial (T2) that were separated by an inter-trial delay of varying lengths. Male PN-COC subjects displayed significantly less time investigating new objects or object locations during T2 in both OR and OP tasks. By contrast, female PN-COC subjects exhibited impairments only in OR and only at the longest inter-trial delay interval. In addition, gestational cocaine increased dendritic spine density in the prefrontal cortex and nucleus accumbens in both genders, but only females had increased spine density in the CA1 region of the hippocampus. These data reveal that in-utero exposure to cocaine results in enduring alterations in anxiety, cognitive function and spine density in adulthood. Moreover, cognitive deficits were more profound in males than in females.

Short- and long-term adverse effects of cocaine abuse during pregnancy on the heart development

The effect of cocaine on the developing fetus is a topic of considerable interest and debate. One of the potential effects of fetal cocaine exposure is damage to the developing heart. This review provides an overview of the current understanding of the short- and long-term effects of fetal cocaine exposure on the heart in both humans and animal models. Human studies are still preliminary but have suggested that fetal cocaine exposure impacts on the developing heart. Studies in animal models provide strong evidence for a programming effect resulting in detrimental long-term changes to the heart induced by fetal cocaine exposure. In the rat model, fetal cocaine results in apoptosis in the term heart, left ventricular remodeling and myocyte hypertrophy, as well as increased sensitivity to ischemia/reperfusion injury in the adult male offspring. The rat model has also shown evidence of epigenetic modifications in response to intrauterine cocaine. Increased DNA methylation of promoter regions leads to a long-term decrease in the expression of the cardioprotective gene, PKCepsilon. The current data shows fetal cocaine exposure has significant immediate and long-term cardiac consequences in animal models and while human studies are still incomplete they suggest this phenomenon may also be significant in humans exposed to cocaine during development.

Perinatal caffeine, acting on maternal adenosine A(1) receptors, causes long-lasting behavioral changes in mouse offspring

BACKGROUND

There are lingering concerns about caffeine consumption during pregnancy or the early postnatal period, partly because there may be long-lasting behavioral changes after caffeine exposure early in life.

METHODOLOGY/PRINCIPAL FINDINGS

We show that pregnant wild type (WT) mice given modest doses of caffeine (0.3 g/l in drinking water) gave birth to offspring that as adults exhibited increased locomotor activity in an open field. The offspring also responded to cocaine challenge with greater locomotor activity than mice not perinatally exposed to caffeine. We performed the same behavioral experiments on mice heterozygous for adenosine A(1) receptor gene (A(1)RHz). In these mice signaling via adenosine A(1) receptors is reduced to about the same degree as after modest consumption of caffeine. A(1)RHz mice had a behavioral profile similar to WT mice perinatally exposed to caffeine. Furthermore, it appeared that the mother's genotype, not offspring's, was critical for behavioral changes in adult offspring. Thus, if the mother partially lacked A(1) receptors the offspring displayed more hyperactivity and responded more strongly to cocaine stimulation as adults than did mice of a WT mother, regardless of their genotype. This indicates that long-term behavioral alterations in the offspring result from the maternal effect of caffeine, and not a direct effect on fetus. WT offspring from WT mother but having a A(1)R Hz grandmother preserved higher locomotor response to cocaine.

CONCLUSIONS/SIGNIFICANCE

We suggest that perinatal caffeine, by acting on adenosine A(1) receptors in the mother, causes long-lasting behavioral changes in the offspring that even manifest themselves in the second generation.

Sex mediates dopamine and adrenergic receptor expression in adult rats exposed prenatally to cocaine

The extent of catecholaminergic receptor and respective behavioral alterations associated with prenatal cocaine exposure varies according to exogenous factors such as the amount, frequency, and route of maternal exposure, as well as endogenous factors such as specific brain regions under consideration and sex of the species. The goal of the current study was to use autoradiography to delineate possible moderators of dopaminergic and adrenergic receptor expression in adult rat offspring exposed to cocaine in utero. The current study demonstrated sex-dependent D1 receptor, alpha2, and noradrenergic transporter binding alterations in prelimbic, hippocampus, and anterior cingulate regions of adult rat brains exposed to cocaine during gestational days 8-21. Of further interest was the lack of alterations in the nucleus accumbens for nearly all receptors/transporters investigated, as well as the lack of alterations in D3 receptor binding in nearly all of the regions investigated (nucleus accumbens, prelimbic region, hippocampus, and cingulate gyrus). Thus, the current investigation demonstrated persistent receptor and transporter alterations that extend well into adulthood as a result of cocaine exposure in utero. Furthermore, the demonstration that sex played a mediating role in prenatal cocaine-induced, aberrant receptor/transporter expression is of primary importance for future studies that seek to control for sex in either design or analysis.

Prenatal cocaine exposure enhances responsivity of locus coeruleus norepinephrine neurons: role of autoreceptors

Children exposed to cocaine during gestation have a higher incidence of neurobehavioral deficits. The neurochemical bases of these deficits have not been determined, but the pharmacology of cocaine and the nature of the abnormalities suggest that disruptions in catecholaminergic systems may be involved. In the current study, we used a rat model of prenatal cocaine exposure to examine the impact that this exposure has on the locus coeruleus (LC) noradrenergic system in offspring. Pregnant rats received twice-daily i.v. injections of cocaine (3 mg/kg) or saline between gestational days 10 and 20, and progeny were tested as juveniles. Exposure to a mild stressor elevated an index of norepinephrine turnover in the prefrontal cortex and also increased Fos expression in tyrosine hydroxylase-positive LC neurons in rats exposed to prenatal cocaine but not in rats exposed to prenatal saline. No change in the number of tyrosine hydroxylase-positive neurons in the LC was observed between the two prenatal treatment groups. Specific binding of [125I]-para-iodoclonidine, a radioligand with specificity for high affinity alpha2A-adrenergic receptors, was decreased in the LC of rats exposed to prenatal cocaine compared with prenatal saline controls. As alpha2-adrenergic receptors on LC norepinephrine neurons function as autoreceptors, their down-regulation by prenatal cocaine exposure provides a plausible mechanism for the observed heightened reactivity of norepinephrine neurons in these animals. These data indicate that prenatal cocaine exposure results in lasting changes to the regulation and responsivity of rat LC norepinephrine neurons. A similar dysregulation of LC norepinephrine neurons may occur in children exposed to cocaine during gestation, and this may explain, at least partly, the increased incidence of cognitive deficits that have been observed in these subjects.

Prenatal cocaine exposure alters alpha2 receptor expression in adolescent rats

BACKGROUND

Prenatal cocaine exposure produces attentional deficits which to persist through early childhood. Given the role of norepinephrine (NE) in attentional processes, we examined the forebrain NE systems from prenatal cocaine exposed rats. Cocaine was administered during pregnancy via the clinically relevant intravenous route of administration. Specifically, we measured alpha2-adrenergic receptor (alpha2-AR) density in adolescent (35-days-old) rats, using [3H]RX821002 (5 nM).

RESULTS

Sex-specific alterations of alpha2-AR were found in the hippocampus and amygdala of the cocaine-exposed animals, as well as an upregulation of alpha2-AR in parietal cortex.

CONCLUSION

These data suggest that prenatal cocaine exposure results in a persistent alteration in forebrain NE systems as indicated by alterations in receptor density. These neurochemical changes may underlie behavioral abnormalities observed in offspring attentional processes following prenatal exposure to cocaine.

Prenatal cocaine exposure: effects on locomotor activity in rat offspring

This study examines the developmental effects of prenatal exposure to cocaine in the rat, evaluated during the first month of life through open-field behavior. The offspring of Wistar dams that received 60mg/kg of cocaine, from gestational day 8 to 22, were examined in the open-field during the second, third and fourth weeks of postnatal life in three consecutive 15-min daily sessions, starting on postnatal day (PND) 14, (PND 14-16), PND 21 (PND 21-23) and PND 28 (PND 28-30). Results show that prenatal exposure to cocaine increased total activity and rearing behavior on PND 22 and PND 29. Also, on PND 14, cocaine-exposed animals reared significantly more than control rats. There were no significant differences in the frequency of center and peripheral ambulation, nor in the defecation rate. The present results evidence alterations in the emotional behavior of rats prenatally exposed to cocaine. The delayed onset of exploration in the open-field observed in cocaine-exposed animals suggests that they take more time to become habituated to a novel and open environment.

Cocaine effects on the developing brain: current status

The present paper reports on the results obtained in a rabbit model of prenatal cocaine exposure that mimics the pharmacokinetics of crack cocaine in humans, and relates these findings to studies in other species including humans. A general finding is that prenatal exposure to cocaine during neurogenesis produces dysfunctions in signal transduction via the dopamine D(1) receptor and alterations in cortical neuronal development leading to permanent morphological abnormalities in frontocingulate cortex and other brain structures. Differences in the precise effects obtained appear to be due to the dose, route and time of cocaine administration. Related to these effects of in utero cocaine exposure, animals demonstrate permanent deficits in cognitive processes related to attentional focus that have been correlated with impairment of stimulus processing in the anterior cingulate cortex. The long-term cognitive deficits observed in various species are in agreement with recent reports indicating that persistent attentional and other cognitive deficits are evident in cocaine-exposed children as they grow older and are challenged to master more complex cognitive tasks.

Presynaptic dopaminergic function is largely unaltered in mesolimbic and mesostriatal terminals of adult rats that were prenatally exposed to cocaine

Fast-scan cyclic voltammetry in brain slices and postmortem tissue content assessment were used to evaluate presynaptic dopaminergic function in the caudate putamen and nucleus accumbens of adult male rats (180+ days old) that were prenatally treated with either cocaine or saline. Experiments were carried out to test whether there were differences in dopamine release, reuptake, autoreceptor function or the tissue levels of dopamine and its metabolites between cocaine- and saline-exposed rats. We report that presynaptic dopaminergic function remains largely intact in adult rats that were prenatally exposed to cocaine. The ability of terminals in the caudate putamen and nucleus accumbens to release and regulate dopamine is unaltered by prenatal cocaine exposure. However the tissue content of dopamine in the caudate putamen was decreased, representing a diminution in the dopamine storage pool. We conclude, therefore, that behavioral changes that have previously been observed in rats that were prenatally exposed to cocaine are not mediated through alteration of presynaptic dopaminergic mechanisms in these brain regions.

Prenatal cocaine exposure alters sensitivity to the effects of idazoxan in a distraction task

The present study was designed to test whether prenatal cocaine (COC) exposure alters sensitivity to the attentional effects of idazoxan (IDZ), an alpha-2 adrenergic antagonist that increases coeruleocortical NE activity. The task assessed subjects' ability to selectively attend to an unpredictable light cue and disregard olfactory distractors. IDZ increased commission errors specifically under conditions of distraction, an effect that was similar in the COC and control groups. In contrast, COC animals were significantly more sensitive than controls to the effects of IDZ on omission errors and nontrials. The pattern of effects suggests that the differential treatment response to IDZ on these latter measures resulted from an alteration in norepinephrine (NE)-modulated dopamine release in the COC animals, reflecting lasting changes in dopaminergic and/or noradrenergic systems as a result of the early cocaine exposure. Based on the behavioral measures that showed a differential response to IDZ in the COC animals, it seems likely that these changes may contribute to the alterations in sustained attention and arousal regulation that have been reported in both animals and humans exposed to cocaine in utero.

Gestational exposure to cocaine or pharmacologically related compounds: effects on behavior and striatal dopamine receptors

Gestational cocaine (COC) exposure has been reported to alter behavior and possibly dopamine (DA) receptors. In this paper, we further examined the effects of prenatal COC (40 mg/kg, s.c.) on DA receptor binding and the behavioral response to quinpirole, a DA D2 receptor agonist. In an attempt to elucidate possible mechanisms of such effects, we exposed pregnant dams to specific reuptake blockers; fluoxetine 12.5 mg/kg, a serotonin reuptake blocker; desipramine 10 mg/kg, a norepinephrine reuptake blocker; GBR-12909 10 mg/kg, a DA reuptake blocker; or to a local anesthetic, lidocaine 40 mg/kg. Drugs were administered once daily over gestational days 8-20. Control dams were injected with saline (SAL) or pair-fed to the COC group. Quinpirole challenge was performed in the offspring on post natal day 19. Two pups per litter were injected (s.c.) with 0.03 or 0.09 mg/kg quinpirole-HCl on post-natal day 19. The remaining pups in each litter were sacrificed for analysis of striatal DA receptors. Results showed that only COC exposure altered the behavioral response to the quinpirole challenge by increasing quinpirole-induced stereotypy and motor activity relative to SAL controls. DA receptor analysis showed no alteration in K(D) or B(MAX) for striatal D1 or D2 sites in any group. These results suggest that prenatal COC exposure produces alterations in function of the D2 receptor complex which are not reflected in K(D) or B(MAX) and that these effects are not fully mimicked by exposure to specific monoamine reuptake blockers or a local anesthetic.

Effects of prenatal exposure to cocaine on the developing brain: anatomical, chemical, physiological and behavioral consequences

Earlier studies of human infants and studies employing animal models had indicated that prenatal exposure to cocaine produced developmental changes in the behavior of the offspring. The present paper reports on the results obtained in a rabbit model of in utero exposure to cocaine using intravenous injections (4 mg/kg, twice daily) that mimic the pharmacokinetics of crack cocaine in humans. At this dose, cocaine had no effect on the body weight gain of dams, time to delivery, litter size and body weight or other physical characteristics of the offspring. In spite of an otherwise normal appearance, cocaine-exposed neonates displayed a permanent impairment in signal transduction via the D1 dopamine receptor in caudate nucleus, frontal cortex and cingulate cortex due to an uncoupling of the receptor from its associated Gs protein. This uncoupling in the caudate nucleus was shown to have behavioral consequences in that young or adult rabbits, exposed to cocaine in utero, failed to demonstrate amphetamine-elicited motor responses normally seen after activation of D1 receptors in the caudate. The cocaine progeny also demonstrated permanent morphological abnormalities in the anterior cingulate cortex due to uncoupling of the D1 receptor and the consequent inability of dopamine to regulate neurite outgrowth during neuronal development. Consistent with the known functions of the anterior cingulate cortex, adult cocaine progeny demonstrated deficits in attentional processes. This was reflected by impairment in discrimination learning during classical conditioning that was due to an inability to ignore salient stimuli even when these were not relevant to the task. The impairment in discrimination learning also occurred in an instrumental avoidance task and could be shown to be due to an impairment of cingulothalamic learning-related neuronal coding. It was proposed that the selective loss of D1-related neurotransmission in the anterior cingulate cortex prevented an appropriate activation of GABA neurons and thus a loss of inhibitory regulation that is necessary for processes involved in associative attention. Taken together, these findings suggest that the uncoupling of the D1 receptor from its G protein may be the fundamental source of the anatomic, cognitive and motor disturbances seen in rabbits exposed to cocaine in utero. Moreover, the long-term cognitive and motor deficits observed in the rabbit model are in agreement with the recent reports indicating that persistent attentional and other behavioral deficits may be evident in cocaine-exposed children as they grow older and are challenged to master more complex cognitive tasks.

Effects of prenatal cocaine exposure on dopamine system development: a meta-analysis

Several studies have investigated the effects of prenatal cocaine (PCOC) exposure on the nigrostriatal dopaminergic system in animal models of maternal drug abuse, yet independent examinations of striatal dopamine (DA) receptors and tissue DA levels have produced equivocal results. The current meta-analysis provides a quantitative review of the literature on these topics, and analyzes potential moderators of the effects of PCOC exposure on these variables. The results indicate that the effects of PCOC exposure on striatal DA levels, D1 and D2 receptor-binding densities, and D2 receptor-binding affinity are negligible when collapsed over age, sex, species, and several other methodological variables. However, effects of PCOC exposure on some dopaminergic measures were significantly influenced by factors such as age and sex. As expected, and as suggested by the selectivity and specificity of PCOC-induced changes reported in the published literature, the direction and magnitude of differences between genders or age groups in this study were not systematic across all dependent measures. Generally, PCOC exposure was more often linked to decreases, rather than increases, in the selected dependent measures. These findings indicate that PCOC exposure produces selective alterations in striatal dopaminergic system function which do not appear under all experimental circumstances, but which may be important factors in behavioral alterations seen in selected groups after PCOC exposure.

Perinatal cocaine exposure impairs myocardial beta-adrenoceptor signaling in the neonatal rat

Cardiac dysfunction occurs in infants with prenatal cocaine exposure, and gestational cocaine exposure induces presynaptic and postsynaptic changes in the central monoaminergic receptor pathways. The hypothesis of this study is that prenatal cocaine exposure adversely affects the peripheral adrenergic receptor (betaAR) signaling pathway in the neonatal rat heart. Timed pregnant rats received daily intragastric treatment with saline or cocaine 20 mg/kg or 60 mg/kg from Gestational Day 2 until parturition. After birth, nursing mothers either continued to receive the same treatment or received no treatment. Adenylyl cyclase activity, betaAR density, and the amount of immunoreactive G proteins were measured in myocardial membranes obtained from the offspring on Postnatal Day 1 or 7. On Postnatal Day 1, prenatal cocaine exposure increased the betaAR number but did not affect isoproterenol-stimulated adenylyl cyclase activity. On Postnatal Day 7, perinatal cocaine exposure significantly attenuated isoproterenol-stimulated adenylyl cyclase activity in the absence of betaAR up-regulation. Prenatal cocaine exposure also significantly increased Gi protein and reduced GTP-stimulated adenylyl cyclase activity in Postnatal Day 1 cocaine (20 mg/kg) pups compared with saline (P < 0.05). Therefore, perinatal cocaine exposure impaired the myocardial betaAR-cAMP signaling pathway during the first week of postnatal life in the rat.

IMPLICATIONS

This study shows that maternal cocaine use during pregnancy impairs the beta-adrenoceptor signaling pathway in the rat during the first week of life. Abnormal cardiac function in the cocaine-exposed neonate may be related to a defect in beta-adrenoceptors, because they regulate cardiac function.

Effects of prenatal cocaine exposure on amphetamine-induced dopamine release in the caudate nucleus of the adult rabbit

Acute amphetamine (AMPH) challenge has been used to probe the neurochemical and behavioral integrity of dopaminergic neurons under various conditions including prenatal cocaine exposure. In this study, we employed in vivo microdialysis to examine the effects of prenatal cocaine exposure on AMPH-induced dopamine (DA) release in the caudate nucleus of the awake adult rabbit. Pregnant rabbits were given intravenous injections of either saline or cocaine (4 mg/kg) twice a day from gestational day 8 (G8) through G29. Microdialysis was performed in adult saline and cocaine progeny at approximately postnatal day 70 (P70). There were no significant differences between cocaine and saline progeny in their basal concentrations of DA or its metabolites, 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA). AMPH (5 mg/kg, i.v.) significantly increased extracellular DA in the caudate of both groups. However, AMPH-induced DA release was 2 to 3-fold greater in cocaine progeny than in the saline controls. Although, DOPAC decreased in both groups following AMPH injection, there was no significant group effect. In addition, there were no significant changes in concentrations of HVA. AMPH is known to release DA by a mechanism of exchange diffusion via the presynaptic DA transporter (DAT). Therefore, we examined the binding of [(3)H]WIN 35,428 to membrane fractions prepared from fresh caudate tissue to determine whether prenatal exposure to cocaine had altered the density (B(max)) or affinity (K(d)) of the DAT. While the B(max) for [(3)H]WIN 35,428 binding increased 3-fold between P3 and P120, there were no significant differences between saline and cocaine progeny at any age examined. The K(d) for [(3)H]WIN 35,428 binding did not change with postnatal age and did not differ between cocaine and saline progeny. These findings suggest that prenatal exposure to cocaine produces a long-term increase in the size of the presynaptic, AMPH releasable, cytoplasmic pool of DA.

Effects of prenatal cocaine exposure on embryonic expression of sonic hedgehog

Cocaine use by pregnant women may adversely affect development and behavior in the exposed infants. Sonic hedgehog (shh) is a secreted protein that induces development of many structures in the embryo, including dopaminergic cells in the ventral midbrain, the limb buds, and eyes. Because prenatal cocaine exposure has been shown to adversely affect the morphogenesis of these and other systems, the present study was undertaken to test the hypothesis that maternal cocaine treatment would alter shh mRNA expression. Cocaine HCl (60 mg/kg i.p.) was administered to pregnant mice on gestational days 6-8, the time that immediately precedes the appearance of shh. Control dams received i.p. saline. Embryos from gestational days 9-11 were examined by in situ hybridization. The temporal and spatial patterns of shh expression were indistinguishable between embryos from cocaine- and saline-treated dams. Examination of forebrain, midbrain, and midbody spinal cord coronal sections failed to reveal any differences in the dorsoventral and mediolateral localization of shh. The distribution of mRNA for patched (ptc), the membrane receptor for shh, was also indistinguishable between both groups. Chick embryos were next used to examine the direct application of cocaine into the developing brain. Shh distribution was similarly unaffected in these chick embryos. These data show that maternal cocaine treatment during early neural tube development does not significantly alter the expression patterns of shh or ptc mRNA. Thus, congenital defects and behavioral abnormalities associated with maternal cocaine use do not appear to result from altered expression of the shh-ptc pathway.

GABAa receptor-mediated field potentials are enhanced in area CA1 following prenatal cocaine exposure

Prenatal cocaine exposure results in several documented changes in neurotransmitter receptor number and structure. Increases have been reported for cortical catecholamine and indoleamine receptor number and binding affinity, in the subunit expression of glutamatergic NMDA and AMPA receptors in the striatum, and in GABA immunoreactivity in the anterior cingulate cortex. We sought information on the functional consequences of cocaine-induced alterations in receptor structure/number. Since hippocampal amino acid neurotransmitters are of critical importance and have been shown to be affected by cocaine, we studied field potentials produced by synaptic activation of isolated glutamatergic NMDA and AMPA receptors and GABAa and GABAb responsive receptors in area CA1 of rabbit hippocampal slices. We found the GABAa receptor population produced significantly larger field potentials in cocaine-exposed offspring compared to controls, while other receptors produced responses similar to controls.

Prenatal effects of drugs of abuse on brain development

Drugs of abuse modify signaling of neurotransmitter systems and intracellular messengers. Recent studies of central nervous system development show that these same neurotransmitters may serve as molecules that regulate specific aspects of cell proliferation, survival, migration, circuit formation and establishment of topography. Moreover, the convergence of neurotransmitter, growth factor and hormone activity on similar intracellular signaling systems suggests the potential for significant interactions among molecular components that regulate development. The application of modern strategies used by developmental and cell biologists to the question of whether prenatal drug exposure alters brain structure and function has led to discoveries of specific, targeted changes. Studies of the mechanisms of drug action that lead to altered neural development are now reality.

Prenatal cocaine exposure increases the reinforcing strength of oral ethanol in C57 mice

Pregnant C57BL/6J mice received daily injections of 10 mg/kg cocaine or saline during gestation days 12-18. Although a previous report indicated that this dose of cocaine did not alter maternal weight gain, birth weight, growth, or adult weight, the present study indicates that it did increase the reinforcing efficacy of ethanol in fully mature male and female offspring. Food-deprived subjects responded on fixed ratio-8 (FR-8) and progressive ratio-2 (PR-2) schedules of reinforcement for 10-, 5-, or 3-s access to various ethanol concentrations. The male prenatal cocaine-exposed mice tended to have higher response totals under the FR-8 schedule and higher breaking-points during some PR-2 tests, with the greatest difference between groups occurring at the highest ethanol concentration. The female prenatal cocaine-exposed mice consumed more ethanol than controls during most of the tests, and had higher breaking-points compared to controls during the more demanding PR-2 tests. Thus, it appears that a dose of cocaine that has no observable effect on many maternal and perinatal outcome measures can alter systems mediating ethanol reward.

The neurobiology of social play behavior in rats

Social play behavior is one of the earliest forms of non-mother-directed social behavior appearing in ontogeny in mammalian species. During the last century, there has been a lot of debate on the significance of social play behavior, but behavioral studies have indicated that social play behavior is a separate and relevant category of behavior. The present review provides a comprehensive survey of studies on the neurobiology of social play behavior. Evidence is presented that opioid and dopamine systems play a role in the reward aspect of social play behavior. The role of cholinergic, noradrenergic and opioid systems in attentional processes underlying the generation of social play behavior and the involvement of androgens in the sexual differentiation of social play behavior in rats is summarized. It is concluded that there is not only behavioral, but also neurobiological evidence to suggest that social play behavior represents a separate category of behavior, instead of a precursor for adult social, sexual or aggressive behavior.

Effects of prenatal cocaine exposure on the mesocorticolimbic dopamine system: an in vivo microdialysis study in the rat

Microdialysis studies were conducted on prenatally saline-treated and prenatally cocaine-treated rats, either as pups (10-30 days old) or young adults (40-190 days old), to study the effects of prenatal cocaine exposure on the mesolimbic dopamine (DA) system. In the n. accumbens of saline-treated rats, basal dialysate concentrations of DA were similar in pups and adults; however, the levels of DA metabolites, DOPAC, HVA, and the serotonin metabolite, 5-HIAA, were markedly lower in pups. In pups, prenatal cocaine exposure led to basal dialysate levels of DA in the n. accumbens that were twice control levels; however, there was no difference in response to a period of intermittent tail pinch or an acute injection of cocaine (20 mg/kg). In the adult, basal levels of DA, DOPAC, HVA and 5-HIAA in n. accumbens did not differ across prenatal treatments. However, in prenatally cocaine-treated adults a cocaine injection led to an enhanced rise in extracellular DA compared to controls. In frontal cortex of adult rats, basal levels of DA, DOPAC and HVA did not differ across prenatal treatments; however, basal levels of 5-HIAA in this region were significantly elevated in prenatal-cocaine rats. No group differences were observed in the frontal cortex in response to either tail pinch or cocaine. Thus prenatal cocaine exposure produces an increase in basal extracellular DA in the n. accumbens of pups which returns to normal with aging. While this initial difference normalizes, prenatal cocaine exposure induces other persistent changes in adulthood.

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.

A murine model of prenatal cocaine exposure: effects on the mother and the fetus

To develop and characterize a murine model for investigating the long-term effects of prenatal cocaine exposure, the present study established the route of drug administration and the doses to be used for pregnant C57BL/6 mice. Comparison of the effects of a high dose of cocaine (60 mg/kg) when gavaged or injected subcutaneously (SC) established patterns of pathology characteristic of administration route but no dominating logic for selecting one over the other route for prenatal studies; however, because of the fourfold greater brain levels, with no evidence of greater pathology, the SC route was selected. When injected daily during gestation days 12-18, the period of prenatal development of dopamine systems, cocaine at doses producing plasma concentrations consistent with its stimulatory effects reduced food ingestion and weight gains during pregnancy and fetal body and brain weights at term. The extent of these reductions was comparable to reports on babies exposed to cocaine prenatally. Furthermore, the present study suggests that maternal undernutrition is not a likely mediator of these perinatal effects and that differences in the amount of cocaine exposure may cause the contrasting effects of maternal cocaine noted in the human literature.

Ethanol self-administration and motor deficits in adults C57BL/6J mice exposed prenatally to cocaine

Daily injections of 10 mg/kg cocaine on gestation days 12-18 did not alter maternal weight gain or offspring birth weight, viability, growth, or adult weight compared to saline controls. Adult male and female offspring were food deprived and trained to lever press for ethanol. Responding on an FR2 schedule and ethanol intake (g/kg) were recorded as measures of the reinforcing effects of ethanol. Lever press duration was used to assess motor performance. Results demonstrate that C57 mice will work for and consume large quantities of ethanol and that prenatal cocaine exposure increased the amounts ingested by both male and female mice. Prenatal-cocaine-exposed males also exhibited motor deficits as indicated by longer response duration times compared to controls. The consumption of large amounts of ethanol exacerbated the motor impairment in prenatal-cocaine males and revealed such deficits in cocaine females. The present results demonstrate that maternal cocaine exposure, at doses having no observable effect upon pregnancy, birth, or offspring growth, can increase the consumption of ethanol and enhance its motor impairing effects on fully mature offspring.

The effects of prenatal cocaine exposure on dopaminergic challenge and receptor binding in Wistar rats

The behavioral teratogenic effects of prenatal cocaine administration in Wistar rats were assessed in dams treated throughout gestation via oral gavage with either 0 or 80 mg/kg of cocaine. A pair-fed (PF) cohort group for the 80-mg/kg dose was used to control for an anorexic effect of cocaine. Alterations in the dopaminergic system at maturity were evaluated using pharmacological challenges with amphetamine and cocaine and by measuring D1 and D2 receptor binding in the nucleus accumbens and caudate nucleus. No significant difference among the offspring of the treatment groups was found in amphetamine-induced locomotion. A cocaine-based conditioned taste aversion was established in all offspring, but no significant effect of prenatal cocaine treatment was seen. Dopamine receptor binding was not significantly influenced by prenatal treatment, although a decreased D1 binding in the caudate nucleus of the prenatal cocaine rats approached significance.

In utero cocaine exposure decreases dopamine D1 receptor modulation of hippocampal long-term potentiation in the rabbit

Cocaine increases the synaptic concentration of neurotransmitters by inhibiting catecholamine transporters. Disturbances of behavior and cellular physiology have been associated with prenatal cocaine exposure and are related to changes in dopamine transmission. Recently we found the magnitude of long-term potentiation (LTP) was greater in hippocampal slices from cocaine exposed offspring. In the hippocampus, D1 dopamine receptor antagonists inhibit the expression of LTP while agonists facilitate it. To test the functionality of the D1 receptor we examined the effect of the D1 antagonist SCH-23390 on LTP using a rabbit model of gestational cocaine exposure. Tetanization during exposure to the D1 antagonist SCH-23390 resulted in a long lasting potentiation in animals prenatally exposed to cocaine while the potentiation of control slices returned to baseline.

Prenatal cocaine exposure leads to enhanced long-term potentiation in region CA1 of hippocampus

Cocaine use by pregnant women is currently of concern for its social and economic impact. Clinical studies of cocaine exposed offspring are limited by methodological constraints. In this study we used a rabbit model to examine the effects of gestational cocaine exposure on substrates of learning and memory. Rabbits, 30 to 40 days old, were examined for alterations in synaptic plasticity using an intact hippocampal slice preparation. Extracellular recordings revealed in utero cocaine exposure predisposed slices to larger long-term potentiation compared to controls.

Prenatal exposure to cocaine selectively disrupts motor responding to D-amphetamine in young and mature rabbits

Acute administration of D-amphetamine probed the functional effects of prenatal exposure to cocaine on the integrity of monoaminergic systems in preweanling (48-56 days old) and adult (> or = 140 days old) Dutch belted rabbits. D-Amphetamine sulfate (0, 0.3, 1.0, 3.3 and 6.0 mg/kg, s.c.) produced equivalent dose-related reductions in food intake in 180 day-old rabbits that had been exposed in utero on gestational days 8-29 to cocaine or saline. Intrauterine exposure to cocaine also did not alter the incidence of exploratory behaviors stimulated by D-amphetamine during the anorexia test. In contrast, however, prenatal cocaine virtually eliminated stereotyped head bobbing elicited by the highest dose of D-amphetamine. When responses to 5.0 mg/kg D-amphetamine were measured during a 90-min open field test, prenatal cocaine prevented head bobbing in preweanling rabbits and reduced this behavior by 92% in 140 day-old adults. Prenatal cocaine also diminished the intensity of other motor responses in the open field in the adults but not in preweanlings. In normal rabbits, the D1 antagonist R(+)-SCH 23390 (0.01 mg/kg, s.c.) blocked D-amphetamine-induced head bobbing. Thus, prenatal exposure to cocaine produces an early and persistent deficit in behavioral responding to a high dose of D-amphetamine. The deficit is especially selective at the time of weaning, broadens to affect more motor behaviors with maturation and may reveal impaired D,-mediated dopaminergic neurotransmission in the brain.

Prenatal cocaine exposure revealed minimal postnatal changes in rat striatal dopamine D2 receptor sites and mRNA levels in the offspring

It has been reported from this laboratory that prenatal cocaine exposure results in the postnatal transient alterations of rat striatal dopamine uptake sites examined from postnatal 0-32 wk. The present study aims to examine whether this will result in a direct/indirect stimulation of dopamine D2 receptors. Pregnant rats were dosed orally with cocaine hydrochloride (60 mg/kg/d) from gestational day (GD) 7-21. Control animals received an equivalent volume of water. The striatum from the offspring at postnatal 0-32 wk was examined. The radioligand [3H]sulpiride was used for the Scatchard analysis of the D2 receptors, and the changes in the levels of mRNA for the D2 receptor were studied using Northern blot analysis. Results from the present study revealed that in the control group, there was an age-dependent increase in the number of D2 receptor sites (Bmax: 44.00 +/- 2.12 to 178.00 +/- 45.10 fmol/mg protein) and in the levels of D2 mRNA from PN0-32 wk with the most rapid increase occurring during the first 4 wk of postnatal development. Prenatal cocaine exposure resulting in only a significant decrease (p < 0.001) in the number of D2 receptor sites at PN0 wk and in a 10% increase in mRNA levels at PN3, 4, and 12 wk. It was concluded from this study that prenatal cocaine exposure resulted in minimal postnatal changes in the dopamine D2 receptor.

Interactive effects of prenatal cocaine and nicotine exposure on maternal toxicity, postnatal development and behavior in the rat

Two experiments were performed to investigate the interactive effects of prenatal coadministration of cocaine hydrochloride (C) and nicotine tartrate (N). Experiment I was designed to determine doses of C and N that could be coadministered without altering maternal gestational parameters and/or fetal viability. Exposure of Sprague-Dawley rats to combined high-dose C (20 mg/kg) and high-dose N (5.0 mg/kg) on gestation days 8-21 was not more toxic to dam or fetus that that of exposure to C alone. Experiment II investigated pregnancy outcome, postnatal development, and behavior of the offspring following drug exposure to either high-dose cocaine (20 mg/kg: CS), high-dose nicotine (5.0 mg/kg: NS), or both (NC) on gestation days 8-21. N was administered by osmotic minipump and C by sc injection. Saline-injected dams, fitted with saline-fitted pumps (SS), and untreated dams, pair-fed (PF) to NC females, served as controls. Alterations in maternal variables were limited to a 10-15% decrease in food consumption in NC and CS groups. Pregnancy outcome and birth statistics were unaffected by prenatal treatment, as was offspring body weight during the first four postnatal weeks. However, the development of surface righting was delayed inC CS pups, and only CS offspring were underresponsive to the stimulatory effects of dopamine agonists on activity and stereotypy. Behavioral responses to N challenge were similar in all groups. In addition, only CS offspring showed altered behavioral responses in a spontaneous alternation task. Treatment effects on dopamine D1 and D2 binding in the caudate nucleus were not observed. The combination of N and C did not exacerbate any of the behavioral changes seen in CS offspring. These results support the hypothesis that C is a behavioral teratogen in rodents, and suggest that in the present model, nicotine can mitigate some of the consequences of in utero exposure to cocaine.

Effects of prenatal cocaine exposure on haloperidol-induced increases in prolactin release and dopamine turnover in weanling, periadolescent, and adult offspring

Offspring of dams given 40 mg/kg cocaine SC on gestational days (GD) 8-20 (E8-20) (C40), dams given 0.9% saline SC on E8-20 that were pair fed and watered to C40 dams (PF), and untreated control dams given ad lib access to food and water (LC) were challenged with haloperidol (0.0, 0.05, 0.10, or 0.50 mg/kg) at either 21, 35, or 60 days postnatally (P21, 35, 60). One hour postinjection, animals were sacrificed, trunk blood collected for assay of prolactin, and the striatum (ST) and nucleus accumbens (NAc) removed. The ratio of the dopamine metabolites 3,4-dihydroxyphenylacetic acid and homovanillic acid to dopamine (DA) as well as the ratio of the serotonin metabolite 5-hydroxyindoleacetic acid (5-HIAA) to serotonin (5-HT) were determined in these brain regions as an index of DA and 5-HT turnover, respectively. Assessment of 5-HIAA/5-HT ratios did not indicate any reliable dose or prenatal treatment effects. Reminiscent of previous findings obtained in C40 offspring at P11 (35), P21 C40 offspring exhibited a slightly reduced sensitivity to haloperidol relative to LC controls both in terms of DA ratios in the NAc as well as plasma prolactin levels. These findings were also evident in PF controls suggesting that they may be the result of prenatal undernutrition. Furthermore, this reduced sensitivity was not evident at the older test ages. At P60, planned comparisons revealed haloperidol-induced increases in prolactin levels in C40 males but not PF or LC males; these findings could potentially reflect feminization in males following prenatal cocaine exposure.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of prenatal exposure to cocaine on heart rate and nonassociative learning and retention in infant rats

Nonassociative learning and retention were assessed in terms of habituation of a heart-rate (HR) orienting response (bradycardia) to a tone in 16-day-old male and female rats prenatally exposed to cocaine and in control offspring. Offspring were derived from Sprague-Dawley dams given daily subcutaneous injections of 40 mg/kg/3 cc cocaine HCI (C40) from gestational days 8-20, pair-fed control dams given saline injections (PF), and nontreated control dams (LC). Each pup was adapted to the test apparatus for 15 min prior to being given 10 presentations of a pulsing tone, each separated by a 65-sec intertrial interval, with HR measured during a 5-sec pretone period and throughout the 10-sec tone for each trial. To assess retention, subjects were given 10 additional tone trials either 1, 2, 4, or 6 hr later. C40 male offspring displayed significantly lower basal HR following the initial 15-min isolation period than either LC or PF offspring, whereas prenatal treatment had no effect on basal HR among females. Although no differences were seen in rate of habituation, prenatal cocaine exposure was observed to affect retention of the habituated orienting response. Whereas LC and PF offspring retained habituation of the orienting response for less than 4 hr, C40 offspring exhibited no forgetting after a 4-hr interval, and showed significant loss of the habituation response only after a 6-hr interval.

Alterations in local cerebral blood flow in mature rats following prenatal exposure to cocaine

Time-mated female Sprague-Dawley rats were injected subcutaneously with either 40 mg/kg cocaine-HCl or saline once daily on gestational days 13 through to 16. Local cerebral blood flow and glucose use were measured in the mature male offspring from these dams using the fully quantitative [14C]2-deoxyglucose and [14C]iodoantipyrine autoradiographic techniques, respectively. The effects of the treatment upon the integrity of central serotonergic terminals was assessed using [3H]paroxetine radioligand binding autoradiography. There were no significant changes in glucose use in any of the 40 brain areas analysed in this study, and although there was a generalized tendency towards increases, these never exceeded +15% of control values. In contrast, significant increases in local cerebral blood flow were measured in more than one-third of the areas examined in cocaine-treated rats, ranging from +20% in dorsal raphe nucleus to +95% in some parts of the neocortex. In all but three brain areas, the ratio of cerebral blood flow to metabolic demand was found to increase following cocaine exposure, resetting the relationship from an overall ratio of 1.6 in controls to 2.5 in treated rats. This relative hyperaemia, which must result from excessive dilatation of the cerebrovascular bed under normal physiological conditions, could not be explained by a direct effect of the treatment on serotonergic constrictor neurons as there was no evidence for any changes in [3H]paroxetine binding. Whatever the underlying cause, we conclude that the effects upon cerebrovascular control mechanisms of prenatal exposure to cocaine identified here, might present a further source of difficulty in the management of "crack babies".

Prenatal exposure to cocaine: effects on aggression in Sprague-Dawley rats

Social/aggressive behavior in adult rat offspring (beginning at postnatal Day 180) prenatally exposed to saline, cocaine, or amfonelic acid (AFA) was examined. Pregnant rats received injections of 15 mg/kg of cocaine, or 0.9% saline twice daily, s.c., or on 2 consecutive days at 4-day intervals, or 1.5 mg/kg amfonelic acid daily throughout gestational Days 1-20. Frequency, duration, and latency of 11 social/aggressive behaviors were recorded for two 15-min sessions during which a smaller male intruder replaced an ovariectomized female in the resident's home cage. Subjects received a s.c. saline injection before Session 1 and 2.0 mg/kg of gepirone, a 5HT1a partial agonist, prior to Session 2. Prenatal cocaine treatment resulted in alterations of aggressive behavior. Aggressive behavior was reduced by gepirone in all groups but to a lesser extent in the AFA group.

Cocaine differentially inhibits neuronal differentiation and proliferation in vitro

The outcome of in utero cocaine exposure is unclear. To determine if cocaine affects neuronal growth and differentiation, we used PC-12 cells, which have a mitogenic response to IGF-I and differentiate into neurons on exposure to nerve growth factor. Differentiation was quantified as neurite extension after a 72-h exposure to 20 ng/ml nerve growth factor (dosage at 50% maximal effectiveness) and cocaine doses ranging from 0.01 to 10 micrograms/ml. The results were 49 +/- 2, 40 +/- 3, 29 +/- 2, 23 +/- 2, and 12 +/- 2% differentiation with respective cocaine concentrations of 0, 0.01, 0.1, 1, and 10 micrograms/ml (P < 0.0001). Cocaine stability studies showed insignificant spontaneous hydrolysis under the conditions of this study. Cocaine did not affect cell viability or number, but had a relatively modest, statistically significant (P < 0.001) inhibitory effect on IGF-I-stimulated thymidine incorporation. The dose-response curves for differentiation vs mitogenic response differed significantly (P = 0.021). Therefore, cocaine inhibition of these processes is probably mediated by different mechanisms, and not caused by generalized toxicity. To our knowledge, this is the first demonstration of cocaine effects on neuronal multiplication and differentiation in vitro. The results suggest in utero exposure may directly impair brain development.