Preweaning cocaine administration alters the adult response to quipazine: comparison with fluoxetine

Sex differences in the effects of cocaine abuse across the life span

Cocaine alters brain function from the early days of development throughout the entire life of an individual. Since the first preclinical research on cocaine sensitization was published, sex differences in response to the drug in adult rats have been noted. With the appearance of reports on "crack babies" during the 1980s, sex differences in response to prenatal (developmental) exposure have been identified in both clinical and preclinical reports. Cocaine administered during early development in the rat produces wide-spread alterations in function which depend on the timing of drug administration as well as the sex of the animal. In males, the response patterns following postnatal days (PND) 11-20 cocaine administration (equivalent to the late prenatal period in humans) are quite similar to those seen following prenatal exposure (equivalent to the first half of pregnancy in humans). There is a general decrease in dopaminergic (DA) markers and reactivity perhaps due to the uncoupling of the D1 receptor from its second messenger system. While similar changes in D1 uncoupling are seen in females, behavioral and metabolic responses to drug challenges generally show increases in DA responsivity (except adolescents) perhaps due to the activational effects of estrogen and/or decreases in serotonin (5-HT) mediated regulation of DA function. We have found that a significant factor in the hyper-responsivity of the female is the role of the testing environment and the responses to stress which can obscure underlying neurochemical dysregulation. Whether parallel factors are operational in adult males and females is currently under investigation.

Fetal effects of psychoactive drugs

Psychoactive drug use by pregnant women has the potential to effect fetal development; the effects are often thought to be drug-specific and gestational age dependent. This article describes the effects of three drugs with similar molecular targets that involve monoaminergic transmitter systems: cocaine, methamphetamine, and selective serotonin re-uptake inhibitors (SSRIs) used to treat maternal depression during pregnancy. We propose a possible common epigenetic mechanism for their potential effects on the developing child. We suggest that exposure to these substances acts as a stressor that affects fetal programming, disrupts fetal placental monoamine transporter expression and alters neuroendocrine and neurotransmitter system development. We also discuss neurobehavioral techniques that may be useful in the early detection of the effects of in utero drug exposure.

Prenatal cocaine use and maternal depression: effects on infant neurobehavior

OBJECTIVE

The present study examined the impact of both perinatal maternal depression and cocaine use on infant neurobehavior at 1 month of age in a large, multi-site study.

METHODS

Infant neurobehavior was examined in 1053 infants at 1 month of age using the NICU Network Neurobehavioral Scale (NNNS). Mothers were interviewed using The Addiction Severity Index to determine present and past psychiatric history. Four groups were derived from the total sample: 385 prenatally cocaine-exposed infants, 76 whose mothers reported current postpartum depression (DEP/COC) and 309 without current postpartum depression (nonDEP/COC); 668 infants were not exposed to cocaine, 104 whose mothers reported current postpartum depression (DEP/nonCOC), 564 without current postpartum depression (nonDEP/nonCOC). A 2x2 Analysis of Covariance was used with covariates (birthweight, maternal age, SES, nicotine, alcohol, and research site) to examine infant neurobehavior in these four conditions. Secondary analyses were conducted to examine the effects of amount and timing of prenatal cocaine exposure.

RESULTS

DEP group by COC exposure status interactions were significant; there was only a DEP effect in the nonCOC infants. Infants in the nonCOC/DEP group had poorer self-regulation and more stress signs, excitability, and arousal than infants in the other groups.

CONCLUSIONS

Postpartum maternal depression has negative effects on infant neurobehavior at 1 month of age. Prenatal cocaine exposure may serve to suppress or buffer the effects of postpartum depression on infant neurobehavior. Maternal mood could explain some of the inconsistencies found in the prenatal cocaine exposure literature.

The effect of developmental exposure to the fungicide triadimefon on behavioral sensitization to triadimefon during adulthood

Triadimefon (TDF) is a triazole fungicide that acts as an indirect dopamine (DA) agonist by binding to the dopamine transporter (DAT) and increasing levels of synaptic DA. Studies in this laboratory have found that repeated dosing with TDF in adult mice leads to the development and robust expression of behavioral sensitization, a response mediated by dopaminergic and glutamatergic neurotransmitter systems, and causing long-term changes in dopaminergic function. Few studies have focused on the potential for TDF to be a developmental neurotoxicant. As such, the objective of the present study was to determine whether postnatal exposure to TDF would permanently alter DA systems and thereby influence TDF-induced expression of behavioral sensitization during adulthood. Male C57BL/6 mice were dosed intraperitoneally (i.p.) with 25 mg/kg TDF (TDF25), or oil (veh) from postnatal day (PND) 8 to 21. At 8-9 weeks of age, mice were split into four groups and treated with 75 mg/kg TDF (TDF75) or vehicle twice a week for a total of seven injections, with locomotor activity measured immediately after each injection. After a 2-week withdrawal period, mice were further split into eight groups, and challenged with TDF75 or vehicle to test for the expression of behavioral sensitization. Postnatal TDF exposure attenuated both the induction and expression of TDF-induced vertical but not horizontal sensitization in adults. Postnatal TDF exposure also produced long-term decreases in basal striatal dihydroxyphenylacetic acid (DOPAC) levels and nucleus accumbens shell DAT binding. These results indicate for the first time that TDF may be considered an environmental risk factor for developmental dopaminergic neurotoxicity.

Structural Effects and Neurofunctional Sequelae of Developmental Exposure to Psychotherapeutic Drugs: Experimental and Clinical Aspects

The advent of psychotherapeutic drugs has enabled management of mental illness and other neurological problems such as epilepsy in the general population, without requiring hospitalization. The success of these drugs in controlling symptoms has led to their widespread use in the vulnerable population of pregnant women as well, where the potential embryotoxicity of the drugs has to be weighed against the potential problems of the maternal neurological state. This review focuses on the developmental toxicity and neurotoxicity of five broad categories of widely available psychotherapeutic drugs: the neuroleptics, the antiepileptics, the antidepressants, the anxiolytics and mood stabilizers, and a newly emerging class of nonprescription drugs, the herbal remedies. A brief review of nervous system development during gestation and following parturition in mammals is provided, with a description of the development of neurochemical pathways that may be involved in the action of the psychotherapeutic agents. A thorough discussion of animal research and human clinical studies is used to determine the risk associated with the use of each drug category. The potential risks to the fetus, as demonstrated in well described neurotoxicity studies in animals, are contrasted with the often negative findings in the still limited human studies. The potential risk fo the human fetus in the continued use of these chemicals without more adequate research is also addressed. The direction of future research using psychotherapeutic drugs should more closely parallel the methodology developed in the animal laboratories, especially since these models have already been used extremely successfully in specific instances in the investigation of neurotoxic agents.

Correlating brain metabolism with stereotypic and locomotor behavior

Many studies have shown that developmental cocaine exposure alters brain function and behavior, the present study examined the relationship between brain metabolism and behavioral responses to drug challenge. SKF 82958, a selective D1 dopamine agonist, was administered to preweaning cocaine-exposed (50 mg/kg/day) rats and controls at 60 days of age. Deoxyglucose was administered 30 min later, during the peak behavioral response, to measure brain functional activity. Pearsonproduct-moment correlations of behavior (locomotor activity and stereotypic behavior) with rates of glucose metabolism in components of the nigrostriatal and mesolimbic circuits were analyzed. The analysis revealed that under saline-challenge conditions in control animals, rates of metabolism in mesolimbic regions are positively correlated to rates of locomotor activity, whereas in cocaine-treated rats, these correlations were absent. Following SKF challenge, a different pattern was seen; locomotor activity or stereotypic behavior was not correlated with mesolimbic or nigrostriatal metabolism, respectively, in controls but was positively correlated in cocaine-treated rats. Therefore, cocaine exposure during development enhances the coupling of metabolism in components of the mesolimbic and nigrostriatal dopamine systems with the behavioral output associated with these systems under drug-challenge conditions. This may be due to loss of inhibitory influences within the mesolimbic and nigrostriatal systems. Thus, the correlation of behavior and cerebral glucose metabolism provides a unique way of examining the effect of developmental cocaine exposure.

Trajectories of brain development: point of vulnerability or window of opportunity?

Brain development is a remarkable process. Progenitor cells are born, differentiate, and migrate to their final locations. Axons and dendrites branch and form important synaptic connections that set the stage for encoding information potentially for the rest of life. In the mammalian brain, synapses and receptors within most regions are overproduced and eliminated by as much as 50% during two phases of life: immediately before birth and during the transitions from childhood, adolescence, to adulthood. This process results in different critical and sensitive periods of brain development. Since Hebb (1949) first postulated that the strengthening of synaptic elements occurs through functional validation, researchers have applied this approach to understanding the sculpting of the immature brain. In this manner, the brain becomes wired to match the needs of the environment. Extensions of this hypothesis posit that exposure to both positive and negative elements before adolescence can imprint on the final adult topography in a manner that differs from exposure to the same elements after adolescence. This review endeavors to provide an overview of key components of mammalian brain development while simultaneously providing a framework for how perturbations during these changes uniquely impinge on the final outcome.

Long-term effects of postnatal amphetamine treatment on striatal protein kinase A activity, dopamine D(1)-like and D(2)-like binding sites, and dopamine content

The purpose of the present study was to determine whether exposure to amphetamine during the preweanling period would alter dopaminergic functioning in the dorsal striatum of adult rats. In three experiments, we assessed the effects of repeated amphetamine treatment on striatal protein kinase A (PKA) activity, dopamine (DA) D(1)-like and D(2)-like binding sites, and DA content. Rats were pretreated with saline or amphetamine (2.5 mg/kg, ip) for 7 consecutive days starting on postnatal day (PD) 11. At PD 90, rats were killed and their dorsal striata (i.e., caudate-putamen) were removed and frozen until time of assay. Amphetamine pretreatment produced long-term reductions in both striatal PKA activity and DA content. Early amphetamine exposure also resulted in an upregulation of D(2)-like binding sites, while leaving D(1)-like binding sites unaffected. It is likely that the upregulation of D(2)-like binding sites was stimulated by the persistent decline in striatal DA levels. Although speculative, it is possible that excess striatal D(2)-like receptors were responsible for inhibiting PKA activity through actions on the cAMP signal transduction pathway. The behavioral relevance of these amphetamine-induced neurochemical changes has not yet be determined.

Evaluation of neonatal exposure to cocaine on learning, activity, startle, scent marking, immobility, and plasma cocaine concentrations

Prenatal cocaine treatment produces equivocal effects on spatial learning and memory; however, no data are available on neonatal treatment as a model of human third-trimester exposure. Sprague-Dawley rats were treated on postnatal days (P) 1-10 or 11-20 with cocaine (15 mg/kg x 4 per day at 2-h intervals) or saline (P1-P20) and evaluated as adults in the Morris water maze and on tests of activity, startle, scent marking, swimming immobility, and sequential learning. Neonatal cocaine had no effect on mortality; however, early treatment reduced body weight, whereas later treatment did not. Neonatal cocaine had no effects on exploratory activity, swimming ability, sequential learning, multiday activity rhythms, scent marking, or swimming immobility, but augmented acoustic startle amplitude in the early-treated group. Neonatal cocaine also produced an interaction on spatial learning in which the cocaine early-treated males performed slightly more efficiently than controls. Plasma cocaine concentrations were significantly higher in the early-treated group than the later-treated group despite receiving the same weight-adjusted doses. It was concluded that neonatal cocaine, when administered during a stage of brain development analogous to human third trimester, induces few behavioral effects based on the assessments used in this study.

Early postnatal cocaine exposure causes sequential, dose-dependent, enduring but reversible supersensitivity in 5-HT2A receptor-mediated function during development in male mice

This report investigated whether postnatal exposure to cocaine affects the index of 5-HT2A receptor function during development by utilizing the ability of the 5-HT2A/C agonist DOI to induce the head-twitch response (HTR) in mice. Thus, several groups of mice litters were treated with varying doses of cocaine (0, 0.5, 1, 5, and 10 mg/kg, IP) twice daily from postnatal days 5 to 14. Then, different groups of cocaine-exposed male mice pups along with their corresponding age-matched vehicle-exposed control groups were HTR tested once during development on the following postnatal test days: 15, 16, 18, 20, 30, 45, and 60. The HTR testing involved administration of DOI (0.5 mg/kg, IP) and counting the frequency of the behavior for the next 20 min. Cocaine exposure caused bell-shaped, dose-dependent, enduring but reversible increase in DOI-induced HTR frequency (mean +/- SEM) during development. The developing pups were most sensitive to low and intermediate doses of cocaine (0.5-5 mg/kg). The greatest degree of increase in HTR frequency in response to DOI challenge occurred in the 1 mg/kg cocaine-exposure group on most test days. The onset of HTR supersensitivity varied from 48 h (5 mg/kg) to 144 h (0.5 mg/kg) following the termination of chronic cocaine exposure. Moreover, maximal supersensitivity for the latter doses of cocaine occurred 96 and 384 h postcocaine treatment, respectively. Other cocaine exposure groups attained their maxima sometime between the latter time periods. The duration of persistence of 5-HT2A receptor supersensitivity varied with different doses of cocaine: the 10-mg/kg group was supersensitive up to 384 h postcocaine treatment, the 1- and 5-mg/kg groups up to 744 h; and the 0.5-mg/kg group up to 1104 h. Although developmentally cocaine-exposed pups exhibit some similarities (i.e., exquisite sensitivity and bell-shaped dose-response) in 5-HT2A receptor adaptation to mature adult mice exposed to cocaine, they also differ from mature adult cocaine-exposed mice in the onset of appearance as well as the enduring persistence of the induced supersensitivity.