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

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 cocaine dampened behavioral responses to methylphenidate in male and female adolescent rats

Clinical and animal data point toward deficits in attention and arousal after prenatal cocaine exposure. Since methylphenidate (MPD) is widely used to treat attention disorders, we wanted to determine whether prenatal cocaine (PC) exposure affects the behavioral response to MPD in young rats of both sexes. Pregnant dams received 60 mg/kg of cocaine or vehicle from gestational days 8-22 by intragastric intubations. After delivery, litters were culled to 10 (5 males, 5 females) and fostered. On a single day between PND 41-44 locomotion was recorded in a Plexiglas box within an Accuscan activity monitor after receiving a single injection of 10 mg/kg intraperitoneally of MPD or saline. Rats were also videotaped for analysis of stereotyped behavior. Results showed that MPD administration enhanced locomotion compared to saline injected groups. PC exposure in male rats did not have any effect on the locomotor response to MPD compared to prenatal controls. However, PC-exposed males showed a lower amount of time spent in low intensity stereotypy compared to prenatal control males and both groups of females that received MPD. PC exposure in female rats that received MPD dampened the locomotor response compared to prenatal control females that also received MPD. In conclusion PC exposure dampens the behavioral response to MPD differentially in males and females with an apparent selectivity of locomotion in females and stereotyped behavior in males.

Sexual dimorphism in the brain metabolic response to prenatal cocaine exposure

The effects of prenatal cocaine exposure on the metabolic function of major central neuronal systems in the periweanling rat are reported in this study. Pregnant Sprague--Dawley rats were administered cocaine at either 30 or 60 mg/kg or the vehicle from gestation day (G) 8 through 22 via daily gastric intubation. Since prenatal cocaine has been shown to alter behavior in weanling rats, brain functional activity was quantified using the deoxyglucose method in male and female 21-day-old offspring (one of each gender/litter). Cocaine's effects were most significant within the limbic system where a three-way interaction between cocaine treatment, sex and brain region was seen. Within the limbic system, two regions, the rostral accumbens and the diagonal band of Broca showed reductions in metabolic activity in the exposed male offspring compared to the control offspring while no changes were seen in females. At more caudal levels of the forebrain, the accumbens (at the level of 1.2 micro rostral to Bregma) and septum showed cocaine-induced reductions in metabolism which were not dependent upon the sex of the animal. Metabolism within the hypothalamus also tended to show a significant interaction between treatment, gender and brain region (P=0.06). Two regions, including the ventromedial nucleus and lateral hypothalamic area, were metabolically depressed in the males alone while three other regions; the dorsomedial, arcuate, and medial preoptic nuclei were also metabolically depressed in the treated groups collapsed across gender. There were no significant treatment or sex-related effects or interactions within the sensory and motor systems. Chronic prenatal cocaine exposure reduced metabolism significantly in a restricted portion of the forebrain, the mesocortical-limbic system, particularly in regions associated with the medial forebrain bundle. These reductions were seen primarily in males while some regions showed changes which were independent of the sex of the animal. These cocaine-induced effects resembled, to a great extent, those seen in similarly-treated males examined as adults. The data emphasize that cocaine use during a restricted period of early pregnancy depresses function within limbic and hypothalamic regions and that many of these effects are sexually dimorphic in nature.

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 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.

Prenatal cocaine exposure alters behavioral and neurochemical sensitization to amphetamine in adult rats

This study examined the neurochemical correlates of amphetamine (AMPH)-induced behavioral effects in prenatally saline (PSAL)-exposed or cocaine (PCOC)-exposed male rats. Pregnant Long-Evans rats received saline or saline containing cocaine hydrochloride (20 mg/kg s.c., b.i.d.) from gestational days 15-21. Animals were left with their biological mothers. Adult offspring were exposed to daily saline or AMPH (0.5, 1.5, or 5 mg/kg, i.p.) injections for 7 days. Behaviors were recorded in an open field during the first hour post-injection. PCOC rats did not exhibit behavioral anomalies during habituation to injection-stress or placement in the open field. PCOC rats displayed significant alterations in stereotyped responses to acute or intermittent exposure to various doses of AMPH. Within 48 h of the final testing day, striatal tissue was obtained from these animals and electrically-evoked [3H]acetylcholine (ACh) release was measured from striatal slices. Superfusion of tissue slices with various concentrations of AMPH (1-1000 nM) produced dose-dependent inhibition of ACh release in both PSAL and PCOC rats repeatedly injected with saline as adults. However, AMPH-induced inhibition of ACh release was decreased in PCOC rats repeatedly injected with AMPH as adults. At 5 mg/kg AMPH, PCOC rats exhibited increased mortality compared to PSAL rats. These data suggest that PCOC exposure produces long-lasting alterations in nigrostriatal transmission and behaviors mediated by this system.