Prenatal cocaine exposure: increased striatal dopamine transporter binding in offspring at 3 and 6 months of age

Cocaine exposure during the early postnatal period diminishes medial frontal cortex Gs coupling to dopamine D1-like receptors in adult rat

The effect of cocaine exposure during early postnatal ages on coupling of dopamine (DA) D(1)- and D(2)-like receptors to their respective Gs/olf and Gi was examined in striatum and medial frontal cortex (MFC). Sprague-Dawley rats were subcutaneously injected with either 50 mg/kg cocaine or vehicle during postnatal day (PnD) 11-20 and dopaminergic D(1)- and D(2)-like receptor signaling was evaluated at PnD 60. Results showed that cocaine exposure did not affect the magnitude of both DA D(1)- and D(2)-like receptor coupling to their respective Gs/olf and Gi in striatum. However, in the medial frontal cortex, the basal and the DA D(1)-like receptor and Gs association were reduced in cocaine-exposed brains. However, there was no change in basal or DA D(2)-like receptor-Gi linkage in medial frontal cortex. Since frontal cortex plays a critical role in regulating cognition and working memory, disruption of DA-modulated circuits or alteration of dopaminergic activity resulting from postnatal cocaine exposure may result in abnormal responses to environmental challenges leading to long-term behavioral changes.

A meta-analysis of animal studies on disruption of spatial navigation by prenatal cocaine exposure

Water-maze testing has been used to assess prenatal cocaine (PCOC)-induced deficits in behavioral studies of spatial navigation and memory abilities. Effects of PCOC in acquisition or in probe trials over water-maze testing days were rarely detected. Despite an absence of effects of PCOC when data were collapsed over multiple days, there was a potential difference when examined during the first day of acquisition training, characterized by a PCOC-associated decrease in learning efficiency but not capacity. Here, we review studies of PCOC-related changes in day-1 water-maze acquisition training and examine the relationship between experimental methodologies and PCOC-treatment procedures and the variability in effect size estimates across studies. The results revealed a significant increase in latencies to goal platform on acquisition training day-1 in PCOC-exposed offspring vs. controls (effect size: r=0.44). Significant effects attributable to variations in the PCOC-treatment procedures across studies were also identified. The moderating variable of PCOC "dose" was significant as lower doses of PCOC exposure yielded larger treatment effects. "Duration" of PCOC exposure was not significant, although a trend for greater effects was observed in studies that employed longer daily treatment schedules or schedules administered in later gestational periods. This analysis identified a consistent difference in acquisition training day-1 of water-maze testing in PCOC-exposed offspring indicating a PCOC-induced deficiency in spatial learning. These findings of impaired spatial learning efficiency are of particular interest given clinical scenarios involving acutely impaired spatial memory and related learning in PCOC-exposed children that highlight the potential consequences in classroom learning.

Gender differences in prodynorphin but not proenkephalin mRNA expression in the striatum of adolescent rats exposed to prenatal cocaine

The objective of this study was to determine if prenatal cocaine affects the levels of prodynorphin and proenkephalin mRNA in male and female adolescent rats. Pregnant dams received cocaine or vehicle from gestational days 8-22 and upon delivery, the pups were fostered. At postnatal days 42-44, pups were killed and brains removed and frozen. Sections of striatum and nucleus accumbens were processed for prodynorphin and proenkephalin mRNA expression. Prenatal cocaine did not affect the expression of proenkephalin mRNA, but males showed higher expression than females. However, prodynorphin mRNA was lower in female rats exposed to cocaine compared to controls. Prenatal cocaine appears to have unique effects on neuropeptides during adolescence.

Attenuation of cocaine-induced genomic and functional responses in prenatal cocaine-exposed rabbits

The effects of in utero cocaine exposure on cocaine-induced genomic and functional responses in postnatal life were examined. Pregnant Dutch Belted rabbits were injected intravenously, twice daily, with cocaine hydrochloride (4 mg/kg) or saline from day 8 through day 29 of pregnancy. Prenatally exposed kits were challenged with cocaine on postnatal day 20. In prenatal saline-exposed kits, cocaine induced time- and dose-dependent c-fos gene expression in both frontal cortex and striatum. Prenatal cocaine exposure reduced cocaine-induced c-fos responses by 35-58% in the frontal cortex and 37-41% in the striatum. Cocaine-induced functional responses that included head bobbing, seizure, and locomotor activity were also attenuated in prenatal cocaine-exposed kits. Cocaine-induced c-fos expression and functional responses were blocked by the D(1) dopamine receptor antagonist, SCH23390, or by the serotonin receptor antagonist, methysergide, but not by the D(2) dopamine receptor antagonist, L-sulpride. The results indicate that in utero cocaine exposure leads to diminished responses to cocaine challenge in the offspring, which may be mediated by prenatal cocaine-induced alterations in one or more components of the D(1) dopamine and/or serotonin receptor signaling systems during early postnatal life.

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.

Neurochemical changes in brain serotonin neurons in immature and adult offspring prenatally exposed to cocaine

The present study investigates the age-dependent effects of prenatal cocaine exposure on changes in the neurochemical and functional status of brain serotonin neurons. Pregnant rats were administered either saline or (-)cocaine HCl (15 mg/kg, subcutaneously), twice daily from gestational days 13 through 20. Neurochemical changes in frontal cortex, hypothalamus, hippocampus, striatum and midbrain of prepubescent and adult offspring were determined by measuring: (1) the content of serotonin (5-HT) and its major metabolite 5-hydroxyindolacetic acid (5-HIAA), and (2) the ability of the serotonin releasing drug p-chloroamphetamine (PCA) to reduce brain serotonin levels. Brain catecholamine content was determined in progeny for comparative purposes. Prior to maturation, prenatal exposure to cocaine did not alter basal levels of brain 5-HT or 5-HIAA in any brain region examined. However, in adult progeny prenatally exposed to cocaine, basal 5-HT content was significantly reduced in the frontal cortex (-32%) and hippocampus (-40%), suggesting maturation-dependent effects of prenatal cocaine exposure on brain 5-HT neurons. Consistent with the maturational onset of changes in 5-HT, striatal dopamine was significantly reduced (-10%) by prenatal exposure to cocaine only in adult offspring. Reductions in 5-HT in most brain regions, produced by pharmacological challenge with p-chloroamphetamine (PCA), were comparable in prenatal saline versus cocaine offspring. One notable exception was the markedly greater reduction (-40%) in 5-HT in the midbrain of immature offspring prenatally exposed to cocaine, suggesting alterations in midbrain 5-HT neurons prior to maturation. Overall, these data demonstrate prenatal cocaine exposure produces region-specific changes in 5-HT neurons in offspring with some deficits occurring only following maturation.

Prenatal cocaine exposure increases serotonergic inhibition of electrically evoked acetylcholine release from rat striatal slices at adulthood

This study tests the hypothesis that prenatal cocaine (pCOC) exposure (20 mg/kg, bidaily from embryonic days 15-21) modifies 5-HT(3) receptor regulation of electrically-evoked [(3)H]acetylcholine (ACh) overflow from adult male and female (proestrus, diestrus) rat striatal slices. Also, the influence of endogenous dopamine (DA) on serotonin (5-HT) regulation of ACh overflow was determined by assessing the effects alpha-methyl-para-tyrosine (AMPT) pretreatment or sulpiride. Phenylbiguanide (PBG, 5-HT(3) agonist) superfusion dose-dependently inhibited ACh overflow in all groups except the diestrus pCOC group in which there was an enhanced sensitivity to PBG. PBG (10, 30, and 60 microM) produced greater effects in the pCOC male than in the prenatal saline (pSAL) group. The pCOC male group also exhibited greater sensitivity to PBG (30 and 60 microM) than the pCOC proestrus group. PBG inhibition of ACh overflow was comparable in the pSAL male and female (proestrus) groups. PBG inhibition of ACh overflow was greater in the pCOC diestrus group than in the pCOC proestrus (10, 30, and 60 microM), the pSAL diestrus (10 and 30 microM), and the pCOC male (10 microM) conditions. In slices from untreated rats superfused with 30 microM PBG, AMPT pretreatment (68% DA loss) reduced inhibition of ACh overflow, and 1 microM sulpiride increased ACh overflow. ICS205-930 (5-HT(3) antagonist) reduced effectiveness of PBG indicating 5-HT(3) receptor specificity for PBG. In summary, pCOC exposure enhances modulatory effects of 5-HT (via 5-HT(3) receptors) on striatal ACh release in male and females rats and the inhibitory actions of 5-HT(3) receptors are mediated by DA.

Perinatal cocaine decreases the expression of prodynorphin mRNA in nucleus accumbens shell in the adult rat

Preprodynorphin mRNA expression in the striatal-olfactory tubercle complex was studied in adult rats exposed to cocaine (50 mg/kg) during postnatal days (PnD) 11-20. While multiple regions of the striatum and olfactory tubercle were examined, alterations were only found in the nucleus accumbens. A 50% and 20% reduction in expression within the shell region was observed at 1.2 and 1.7 mm rostral to Bregma respectively. While the core regions at these levels were unaffected, the rostral accumbens showed a trend toward an increase in expression in the cocaine-treated rats. These findings, in combination with other behavioral and neurochemical data collected on similarly treated rats, suggest that perinatal cocaine produces a long-term dampening of function in a specific population of neurons within the mesolimbic system

Human placental norepinephrine transporter mRNA: expression and correlation with fetal condition at birth

The purpose of this study was to determine the primary form of human placental norepinephrine transporter (hNET) mRNA expressed in the human placenta and to compare the level of expression in normal pregnancies and in pregnancies complicated by drug exposure or other forms of physiological derangement. We used the hNET cDNA to measure RNA extracted from placenta and examined placental RNA following complicated and uncomplicated pregnancies. To compare transporter expression and its relation to fetal condition at birth, umbilical arterial plasma catecholamine levels, umbilical arterial blood gases and placental transporter mRNA level were compared by linear regression analysis. Uncomplicated pregnancies had a higher level of placental norepinephrine transporter mRNA than complicated pregnancies. An inverse relationship between umbilical cord norepinephrine level and transporter expression was demonstrated. We conclude that placental transporter expression represents an important and newly described metabolic function of the placenta. Placental catecholamine clearance mediated via the placental NET may be important in the pathophysiology of disorders associated with placental dysfunction, impaired placental blood flow or intrauterine growth retardation. This may also explain the adverse effects of drugs, such as cocaine, which block catecholamine transport.

Monoamine transporters and the neurobehavioral teratology of cocaine

Prenatal cocaine exposure has been associated with various postnatal behavioral abnormalities in human infants, and also with changes in locomotor activity, learning deficits, and altered responses to drug challenge in nonhuman offspring. Several studies have further demonstrated that cocaine exerts an activating effect on fetal behavior. A variety of mechanisms have been proposed to account for the neurobehavioral teratogenic effects of developmental cocaine treatment, including inhibition of fetal brain neurotransmitter uptake and fetal hypoxemia secondary to constriction of the uteroplacental vascular bed. In support of the hypothesis that cocaine effects may be mediated partly by monoamine uptake inhibition, we and other investigators have recently demonstrated the presence of functional dopamine (DA), serotonin (5-HT), and norepinephrine (NE) transporters in the fetal rat brain. Transporter-related cocaine recognition sites are found in a number of fetal brain areas and could mediate the acute effects of cocaine on these areas as well as developmental changes that are manifested postnatally. For example, DA transporter blockade may underlie the above-mentioned activational effects of cocaine on fetal behavior. Time-dependent changes in DA or 5-HT transporter expression produced by prenatal cocaine exposure could likewise play an important role in some of the behavioral effects observed when offspring are tested postnatally.

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.

Prenatal cocaine: effect on hypoxic ventilatory responsiveness in neonatal rats

The effects of prenatal (embryonic days 7-21) cocaine (30 mg/kg b.i.d., s.c.) exposure on postnatal respiratory and behavioral responsiveness to acute hypoxia were investigated in 5-day-old (P5) rat pups. Control and cocaine-exposed pups were subjected to 20 min of 0.21 FIO2 followed by 20 min of 0.08 FIO2. Although all pups demonstrated the characteristic biphasic response to hypoxia, cocaine-exposed pups exhibited a blunted, initial response in minute ventilation (p < 0.05) and inspiratory drive (p < 0.05) as compared with control pups who showed increases in these measures (p < 0.01 and p < 0.05, respectively). The consequence of this apparent blunted ventilatory response was reflected in blood gas data gathered after 20 min of 0.08 FIO2:PCO2 (p < 0.05) and base-excess (p < 0.05) were increased and HCO3- (p < 0.05) and SO2 (p < 0.01) were decreased relative to control pups. Cocaine-exposed pups also exhibited behavioral evidence of decreased struggling (p < 0.001) in response to the hypoxic challenge. These data in the rat confirm our previous findings of altered ventilatory responsiveness to inspired hypoxia in the rabbit and extend our observations of a decreased ability to successfully compensate and behaviorally arouse following prenatal cocaine-exposure, thus underscoring the potential vulnerability of infants so exposed.

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.

Effects of in utero cocaine exposure on the expression of mRNAS encoding the dopamine transporter and the D1, D2 and D5 dopamine receptor subtypes in fetal rhesus monkey

The effects of in utero cocaine exposure on the development of the mRNAs encoding the dopamine transporter (DAT) and the D1, D2 and D5 dopamine receptor subtypes were determined in fetal monkey brains at day 45 and day 60 of gestation. Pregnant monkeys were treated with cocaine 3 mg/kg or saline i.m., four times a day from day 18 of gestation until the pregnancy was terminated at day 45 or day 60. The fetal brains were dissected, and tissue RNA extracted and quantified using ribonuclease protection assay analysis. In day 45 fetal monkeys, dopamine D1 and D2 receptor subtype mRNAs and DAT mRNA were found in low quantities both in control and cocaine-treated subjects. In day 60 fetal monkeys, D1 receptor mRNA levels were highest in the frontal cortex/striatal area, and low to moderate quantities were found in diencephalic and mesencephalic fetal brain regions. Dopamine D2 receptor mRNA levels were highest in the frontal cortex/striatal area, diencephalon and the midbrain, moderate in the brainstem and low in the caudal temporal lobe and surrounding cortical areas. Dopamine D5 receptor mRNA was expressed in low quantities throughout the day 60 fetal monkey brain, whereas DAT mRNA was found in the midbrain only. In utero cocaine exposure caused a significant increase in dopamine D1, D2 and D5 receptor subtype mRNAs in the frontal cortex/striatal area of day 60 fetal monkeys. These results support the hypothesis that dopamine synthesis and release may be reduced in cocaine-treated fetuses, which results in dopamine receptor up-regulation.

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)