Diana L. Dow-Edwards

Structural and functional effects of prenatal cocaine exposure in adult rat brain

The long-term effects of cocaine exposure early in development on the metabolic function of major central neuronal systems in the rat are reported in this study. Pregnant Wistar rats were administered either 60 mg/kg cocaine or the vehicle from gestation day (G) 8 through 22 via daily gastric intubation. Sixty-day-old male offspring were examined using the quantified deoxyglucose autoradiographic method. Of the 45 structures examined, 2 cortical and 14 subcortical structures showed statistically significant alterations in glucose metabolism compared to controls. The primary somatosensory and motor cortices showed significant decreases. The hypothalamus contained the greatest concentration of nuclei showing significant changes in activity. All of these changes were decreases. The nigrostriatal pathway, the medial forebrain bundle, the hippocampus, septum and amygdala were all significantly less metabolically active in the exposed offspring. The subcortical sensory systems did not appear to be affected at the dose of cocaine studied. Adjacent sections incubated in 1nM [3H]SCH 23390 showed an increase in the concentration of D1 receptors in the substantia nigra, pars reticulata. Forebrain dopaminergic regions which showed decreased glucose metabolism did not appear to have altered SCH 23390 binding. Although size determinations were made on several cortical and subcortical structures, none were significantly affected by prenatal cocaine. Effects of chronic prenatal cocaine exposure on adult brain metabolism in several neuronal systems were identified at doses which had no significant effects on adult brain or body size. These data support the hypothesis that cocaine use during pregnancy produces permanent neurological effects at doses below those which produce growth retardation and terata.

Preferential limbic expression of the cannabinoid receptor mRNA in the human fetal brain

The cannabinoid receptor one (CB1) is responsible for the effects of cannabis on motor and cognitive function in the CNS. There is to date very limited information about the CB1 gene expression in the human brain, in particular during fetal development. In the present study, in situ hybridization experiments were used to examine the microscopic and macroscopic organization of the CB1 mRNA expression in normal human fetal (approximately 20 weeks of development) and adult brains. The fetal brain showed a distinct heterogeneous pattern of the CB1 mRNA expression which was low to moderate in many brain areas. The most striking feature of the fetal brain was the intense expression in the hippocampal CA region and basal nuclear group of the amygdaloid complex. Many of the same brain areas that showed positive expression of the CB1 mRNA in the fetal brain also expressed the gene in the adult brain. However, aside from an intense expression in the hippocampus which resembled that in fetal brain, the adult brain showed very high expression throughout the cerebral cortex, caudate nucleus, putamen and cerebellar cortex. These results document a different pattern of the anatomical organization of the CB1 mRNA expression in the mid-gestation fetal and adult human brain. Overall, the high CB1 mRNA expression in the fetal hippocampus and amygdala indicates that these limbic structures might be most vulnerable to prenatal cannabis exposure.

Stimulation of brain metabolism by perinatal cocaine exposure

Cocaine was administered to neonatal rats between day 1 and day 10, which in the rat falls within a developmental stage roughly equivalent to the third trimester of gestation in human fetuses. At 60 days of age, when the animals had reached adulthood, cerebral glucose metabolic patterns were examined by quantitative autoradiography. Adult females, but not adult males, exhibited significant increases in metabolic activity in a number of cerebral structures, including those of the limbic, motor, and sensory systems. Many of these structures are the same as those which are excited in adult rats by the acute administration of cocaine and other stimulants. These data suggest that cocaine consumption during pregnancy may constitute a risk factor leading to long-term alterations in brain function in the adult.

Structural and metabolic alterations in rat cerebral cortex induced by prenatal exposure to ethanol

The effects of prenatal exposure to ethanol on glucose utilization in specific laminae of mature rat cerebral cortex were examined. Pregnant hooded rats were fed a liquid diet containing 35% ethanol-derived calories (E) or pair-fed an isocaloric liquid control diet (C) on gestational days 7-21. The cytoarchitecture of motor areas 4 and 6/8 and of somatosensory areas 3 and 2 of 105 day old, male pups was examined in Cresyl violet-stained sections. The glucose utilization of these cortical regions was assessed using a 2-deoxyglucose autoradiographic technique. Overall, cortex was significantly thinner (5-10%) in E-treated rats than in C-treated rats, but with few exceptions, the thickness of individual laminae was not significantly affected by prenatal treatment. Despite these small structural differences, the overall glucose utilization in areas 4, rostral 6/8 3, and 2 of E-treated rats was significantly less (21-24%) than in C-treated rats. Layer IV was the most affected by the prenatal ethanol exposure (29%) and layers I and VI were the least affected (14-22%). The metabolism of caudal area 6/8 was not significantly affected by gestational exposure to ethanol. These results indicate that thalamic and callosal connections and corticospinal projection neurons are specifically affected by prenatal exposure to ethanol. Such alterations may underlie the learning deficits and motor dysfunction characteristic of fetal alcohol syndrome.

In utero marijuana exposure associated with abnormal amygdala dopamine D2 gene expression in the human fetus

BACKGROUND Marijuana (Cannabis sativa) is the illicit drug most used by pregnant women, and behavioral and cognitive impairments have been documented in cannabis-exposed offspring. Despite the extensive use of marijuana, very limited information exists as to the consequences of prenatal cannabis exposure on the developing human brain. METHODS We optimized an in situ hybridization histochemistry technique to visualize mRNA expression in midgestation (weeks 18-22) human fetal specimens from mothers with and without documented evidence of cannabis use during pregnancy. The cannabinoid receptor type 1 (CB(1)) and major dopamine receptor subtypes, D(1) and D(2), were examined in the striatum and mesocorticolimbic structures (amygdala and hippocampus). RESULTS Adjusting for various covariates, we found a specific reduction, particularly in male fetuses, of the D(2) mRNA expression levels in the amygdala basal nucleus in association with maternal marijuana use. The reduction was positively correlated with the amount of maternal marijuana intake during pregnancy. No significant cannabis-related alterations were detected in the hippocampus or caudal striatum for the D(2), D(1), and CB(1) mRNA levels, although alcohol showed significant contribution to striatal D(1)/D(2) expression. CONCLUSIONS These human fetal findings suggest that in utero cannabis exposure may impair distinct mesocorticolimbic neural systems that regulate emotional behavior.

Comparison of oral and subcutaneous routes of cocaine administration on behavior, plasma drug concentration and toxicity in female rats

Oral and subcutaneous routes of administration of cocaine HCl were investigated in female Wistar rats for food and water consumption, locomotor activity, stereotypic behaviors, plasma drug concentrations and injection site pathology. Animals received either 40 or 80 mg/kg/day by gastric intubation (PO-40 and PO-80 respectively) or 20 or 40 mg/kg/day subcutaneously (SC-20 and SC-40). All groups received the drug or the vehicle for 16 consecutive days. Locomotor activity and stereotypy were evaluated on Days 1, 5, 10, and 15. Plasma drug concentrations and injection site pathology were determined on Day 16. Subcutaneous administration was associated with a sensitization to the effects of cocaine on locomotion and stereotypy, higher blood levels than oral administration at the same dose, and severe dermal lesions. However, there were no differences in any measure between the SC-20 and SC-40 groups. Oral cocaine was also associated with behavioral sensitization. However, unlike the SC route, oral cocaine was characterized by dose-related increases in locomotion and stereotypy in the absence of gastrointestinal pathology. Inasmuch as oral administration resulted in dose-response relationships and low toxicity while subcutaneous administration did not, these factors should be considered in future studies utilizing chronic cocaine administration.

Cocaine treatment in neonatal rats affects the adult behavioral response to amphetamine

This study investigated whether exposure to cocaine during critical periods of brain development alters the motor stimulating effects of amphetamine given in adulthood. Female rats received 50 mg/kg/day cocaine HCl SC or vehicle during either postnatal days 1-10 or 11-20. At 60-65 days of age, activity counts were collected over a 15-min baseline period. Subjects then received one of 3 doses (0, 0.1, 0.25 mg/kg) of d-amphetamine sulfate SC followed by a 90-min period of activity monitoring. Adult activity in 1-10-day cocaine-treated rats was different from vehicle-treated rats in response to 0.1 mg/kg amphetamine only. Adult activity in 11-20-day cocaine-treated rats was different from vehicle-treated rats in response to 0.25 mg/kg only. The observed differences represented an increase and decrease in activity, respectively. These alterations in amphetamine response may be related to the observed alterations in D-1 receptor concentrations as well as the altered rates of brain glucose metabolism we have observed in adult rats neonatally exposed to cocaine.

Long-term alterations in brain function following cocaine administration during the preweanling period.

This report examines the long-term effects of cocaine exposure during postnatal days (P) 11-20 on the metabolic function of major central neuronal systems. Cocaine (50mg/kg) or vehicle was administered subcutaneously to rat pups during P 11-20. At 60-64 days of age, the rats were examined for cerebral glucose metabolic patterns. In cocaine-treated females 18 of the 46 structures evaluated showed increased metabolic rates including 5 of 6 structures within the motor system and 7 of 17 limbic structures. No decreased rates were seen. In males, cocaine had no effects in the motor structures or hypothalamus while 2 of 17 structures within the limbic system showed decreased rates of glucose utilization and 2 of 11 structures within the sensory systems showed increased rates. These results indicate that female rats show greater long-term metabolic effects than males and that cocaine exposure during P 11-20 produces different metabolic effects than cocaine exposure during P 1-10 which we previously reported.

Fetal and maternal cocaine levels peak rapidly following intragastric administration in the rat

On gestation day 22, plasma levels of cocaine and its metabolite, benzoylecgonine (BE), were determined over 90 min following either 30 or 60 mg/kg cocaine given via intragastric intubation to Wistar rats which had been given daily cocaine intubations since day 8 of pregnancy. Cocaine levels peaked at 15 min in both the maternal and fetal circulations. Sixty mg/kg produced a peak plasma level of 5384 +/- 594 ng/ml in the dam and 2966 +/- 503 ng/ml in the fetus. Maternal levels of cocaine were higher than fetal levels for the first fifteen min. Thereafter, maternal levels decreased more quickly than fetal such that at 30-90 min, fetal levels were higher than maternal levels. Cocaine levels also peaked at 15 min in fetal brain. At 90 min, however, fetal brain had between 26 and 42% more cocaine than fetal plasma. Therefore, fetal brain exposure to cocaine is somewhat prolonged. BE levels were less predictable. Together, these data indicate that the intragastric route of administration results in rapid uptake of cocaine by blood and produces highly reproducible, pharmacologically relevant levels of cocaine in maternal and fetal plasma and brain. In addition, the placenta does not act as a barrier to the delivery of cocaine to the fetus.

Differential behavioral responses to chronic amphetamine in adult male and female rats exposed to postnatal cocaine treatment.

The impact of cocaine exposure during development on behavioral sensitization as measured by locomotor activity and stereotypy following repeated intermittent administration of amphetamine is examined. Male and female Sprague-Dawley rats were exposed to cocaine at 50 mg/kg/day during postnatal days (PND) 11-20 and, as adults (PND193-212), were administered seven daily injections of 2.0 mg/kg amphetamine. Both locomotor activity and stereotypic behavior were assessed following the first and seventh injections. Control males and females showed sensitized behavior following repeated amphetamine injections with females showing greater locomotion while males showed increased stereotypy. Male rats pretreated with cocaine failed to develop sensitized locomotor or stereotypic responses following repeated amphetamine injections consistent with dampened D(1) receptor activity. Females pretreated with cocaine did not show a sensitized locomotor response but did display sensitization of stereotypy following repeated amphetamine administration. Thus, it appears that postnatal cocaine treatment produces differential effects on the circuits mediating sensitization behavior in male and female rats.