Differing neurotoxic potencies of methamphetamine, mazindol, and cocaine in mesencephalic cultures

Acute psychiatric illness and drug addiction during pregnancy and the puerperium

Pregnancy and the puerperium do not protect against acute psychiatric illness. During puerperium, the chance of acute psychiatric illness, such as a psychotic episode or relapse of bipolar disorder, is greatly increased. Suicide is a leading cause of maternal death. Both psychiatric disease and ongoing drug addiction impact not only the pregnant woman's somatic and mental health but also impact short-term and long-term health of the child. Indeed, prompt recognition and expeditious treatment of acute psychiatric illness during pregnancy and the puerperium optimize health outcomes for two patients. Pregnancy and puerperium represent a stage of life of great physiologic adaptations, as well as emotional and social changes. This conjunction of changes in somatic, emotional health and social health may mitigate the occurrence, clinical presentation, and clinical course of acute psychiatric illness and call for a multidisciplinary approach, taking into account both the medical and social domains. This chapter describes acute psychiatric illnesses during pregnancy and the puerperium and illicit substance abuse, from a clinical perspective, while also describing general principles of diagnosis and clinical management during this stage of life, which is an important window of opportunity for both the pregnant woman and the child.

Identification of cytotoxic markers in methamphetamine treated rat C6 astroglia-like cells

Methamphetamine (METH) is a powerfully addictive psychostimulant that has a pronounced effect on the central nervous system (CNS). The present study aimed to assess METH toxicity in differentiated C6 astroglia-like cells through biochemical and toxicity markers with acute (1 h) and chronic (48 h) treatments. In the absence of external stimulants, cellular differentiation of neuronal morphology was achieved through reduced serum (2.5%) in the medium. The cells displayed branched neurite-like processes with extensive intercellular connections. Results indicated that acute METH treatment neither altered the cell morphology nor killed the cells, which echoed with lack of consequence on reactive oxygen species (ROS), nitric oxide (NO) or inhibition of any cell cycle phases except induction of cytoplasmic vacuoles. On the other hand, chronic treatment at 1 mM or above destroyed the neurite-like processors and decreased the cell viability that paralleled with increased levels of ROS, lipid peroxidation and lactate, depletion in glutathione (GSH) level and inhibition at G0/G1 phase of cell cycle, leading to apoptosis. Pre-treatment of cells with N-acetyl cysteine (NAC, 2.5 mM for 1 h) followed by METH co-treatment for 48 h rescued the cells completely from toxicity by decreasing ROS through increased GSH. Our results provide evidence that increased ROS and GSH depletion underlie the cytotoxic effects of METH in the cells. Since loss in neurite connections and intracellular changes can lead to psychiatric illnesses in drug users, the evidence that we show in our study suggests that these are also contributing factors for psychiatric-illnesses in METH addicts.

The cellular basis of fetal endoplasmic reticulum stress and oxidative stress in drug-induced neurodevelopmental deficits

Prenatal substance exposure is a growing public health concern worldwide. Although the opioid crisis remains one of the most prevalent addiction problems in our society, abuse of cocaine, methamphetamines, and other illicit drugs, particularly amongst pregnant women, are nonetheless significant and widespread. Evidence demonstrates prenatal drug exposure can affect fetal brain development and thus can have long-lasting impact on neurobehavioral and cognitive performance later in life. In this review, we highlight research examining the most prevalent drugs of abuse and their effects on brain development with a focus on endoplasmic reticulum stress and oxidative stress signaling pathways. A thorough exploration of drug-induced cellular stress mechanisms during prenatal brain development may provide insight into therapeutic interventions to combat effects of prenatal drug exposure.

Cocaine Causes Apoptotic Death in Rat Mesencephalon and Striatum Primary Cultures

To study cocaine's toxic effects in vitro, we have used primary mesencephalic and striatal cultures from rat embryonic brain. Treatment with cocaine causes a dramatic increase in DNA fragmentation in both primary cultures. The toxicity induced by cocaine was paralleled with a concomitant decrease in the microtubule associated protein 2 (MAP2) and/or neuronal nucleus protein (NeuN) staining. We also observed in both cultures that the cell death caused by cocaine was induced by an apoptotic mechanism, confirmed by TUNEL assay. Therefore, the present paper shows that cocaine causes apoptotic cell death and inhibition of the neurite prolongation in striatal and mesencephalic cell culture. These data suggest that if similar neuronal damage could be produced in the developing human brain, it could account for the qualitative or quantitative defects in neuronal pathways that cause a major handicap in brain function following prenatal exposure to cocaine.

Cocaine abuse in humans is not associated with increased microglial activation: an 18-kDa translocator protein positron emission tomography imaging study with [11C]PBR28

Basic science investigations have consistently shown that repeated exposure to psychostimulant drugs, such as cocaine, activate the immune response and lead to inflammatory changes in the brain. No previous in vivo studies have confirmed this observation in chronic cocaine-abusing humans. To test this hypothesis, we used positron emission tomography imaging to measure the binding of [(11)C]PBR28 to the 18 kDa translocator protein (TSPO), a marker for microglial activation in a group of 15 recently abstinent cocaine abusers and 17 matched healthy controls. [(11)C]PBR28 volumes of distribution expressed relative to total plasma ligand concentration (VT) were measured in subjects with kinetic analysis using the arterial input function. Subjects were also genotyped for the TSPO alanine147 threonine (Ala147Thr, rs6971) polymorphism that has been shown to influence the in vivo binding of PBR28 to TSPO. Consistent with previous reports, the TSPO Ala147Thr genotype predicted the in vivo binding of [(11)C]PBR28. No significant differences in [(11)C]PBR28 VT were observed in the cortical and subcortical regions in cocaine abusers compared with healthy controls. The results of this in vivo study do not support increased TSPO expression and, by extension, microglial activation in chronic cocaine-abusing humans. Further research with more direct markers of microglial activation is necessary to conclusively rule out neuroinflammation in cocaine dependence.

The effects of psychostimulant drugs on blood brain barrier function and neuroinflammation

The blood brain barrier (BBB) is a highly dynamic interface between the central nervous system (CNS) and periphery. The BBB is comprised of a number of components and is part of the larger neuro(glio)vascular unit. Current literature suggests that psychostimulant drugs of abuse alter the function of the BBB which likely contributes to the neurotoxicities associated with these drugs. In both preclinical and clinical studies, psychostimulants including methamphetamine, MDMA, cocaine, and nicotine, produce BBB dysfunction through alterations in tight junction protein expression and conformation, increased glial activation, increased enzyme activation related to BBB cytoskeleton remodeling, and induction of neuroinflammatory pathways. These detrimental changes lead to increased permeability of the BBB and subsequent vulnerability of the brain to peripheral toxins. In fact, abuse of these psychostimulants, notably methamphetamine and cocaine, has been shown to increase the invasion of peripheral bacteria and viruses into the brain. Much work in this field has focused on the co-morbidity of psychostimulant abuse and human immunodeficiency virus (HIV) infection. As psychostimulants alter BBB permeability, it is likely that this BBB dysfunction results in increased penetration of the HIV virus into the brain thus increasing the risk of and severity of neuro AIDS. This review will provide an overview of the specific changes in components within the BBB associated with psychostimulant abuse as well as the implications of these changes in exacerbating the neuropathology associated with psychostimulant drugs and HIV co-morbidity.

Human dental pulp stem cells protect mouse dopaminergic neurons against MPP+ or rotenone

Parkinson's disease (PD) is a neurodegenerative disorder characterized by the progressive death of substantia nigra dopaminergic neurons that results in a regional loss of striatal dopamine (DA) levels. Dental pulp contains ex vivo-expandable cells called dental pulp stem cells (DPSCs), with the capacity to differentiate into multiple cell lineages. More interestingly, due to their embryonic origin, DPSCs express neurotrophic factors such as brain-derived neurotrophic factor, nerve growth factor and glial cell-derived neurotrophic factor. The aim of the present study was to investigate the neuroprotective effects of DPSCs against MPP+ (2.5, 5, and 10 μM) and rotenone (0.25, 0.5 and 1 μM) in an in vitro model of PD, using an indirect co-culture system with mesencephalic cell cultures. When mesencephalic cultures were challenged with MPP+ or rotenone, in the presence of DPSCs a statistically significant protective effect was observed at all the tested doses in terms of DA uptake. DPSCs protective effect on DA neurons was also confirmed by immunocytochemistry: an increased number of spared tyrosine hydroxylase (TH)+ cells was observed in co-culture conditions compared to controls, and neurons showed longer processes in comparison with mesencephalic cells grown without DPSCs. In conclusion, the co-culture with DPSCs significantly attenuated MPP+ or rotenone-induced toxicity in primary cultures of mesencephalic neurons. Considering that the direct contact between the two cell types was prevented, it can be speculated that neuroprotection could be due to soluble factors such as BDNF and NGF, released by DPSCs. Blocking BDNF and NGF with neutralizing antibodies, the neuroprotecting effect of DPSCs was completely abolished. Therefore DPSCs can be viewed as possible candidates for studies on cell-based therapy in neurodegenerative disorders.

Prenatal methamphetamine exposure and neonatal neurobehavioral outcome in the USA and New Zealand

BACKGROUND

Methamphetamine (MA) use among pregnant women is a world-wide problem, but little is known of its impact on exposed infants.

DESIGN

The prospective, controlled longitudinal Infant Development, Environment and Lifestyle (IDEAL) study of prenatal MA exposure from birth to 36 months was conducted in the US and NZ. The US cohort has 183 exposed and 196 comparison infants; the NZ cohort has 85 exposed and 95 comparison infants. Exposure was determined by self-report and meconium assay with alcohol, marijuana, and tobacco exposures present in both groups. The NICU Neurobehavior Scale (NNNS) was administered within 5 days of life. NNNS summary scores were analyzed for exposure including heavy exposure and frequency of use by trimester and dose-response relationship with the amphetamine analyte.

RESULTS

MA exposure was associated with poorer quality of movement, more total stress/abstinence, physiological stress, and CNS stress with more nonoptimal reflexes in NZ but not in the USA. Heavy MA exposure was associated with lower arousal and excitability. First trimester MA use predicted more stress and third trimester use more lethargy and hypotonicity. Dose-response effects were observed between amphetamine concentration in meconium and CNS stress.

CONCLUSION

Across cultures, prenatal MA exposure was associated with a similar neurobehavioral pattern of under arousal, low tone, poorer quality of movement and increased stress.

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.

Involvement of nicotinic receptors in methamphetamine- and MDMA-induced neurotoxicity: pharmacological implications

During the last years, we have focused on the study of the neurotoxic effects of 3,4-methylenedioxymethamphetamine (MDMA) and methamphetamine (METH) on the central nervous system (CNS) and their pharmacological prevention methods. In the process of this research, we have used a semipurified synaptosomal preparation from striatum of mice or rats as a reliable in vitro model to study reactive oxygen species (ROS) production by these amphetamine derivatives, which is well-correlated with their dopaminergic injury in in vivo models. Using this preparation, we have demonstrated that blockade of alpha7 nicotinic receptors with methyllycaconitine (MLA) prevents ROS production induced by MDMA and METH. Consequently, in vivo, MLA significantly prevents MDMA- and METH-induced neurotoxicity at dopaminergic level (mouse striatum), without affecting hyperthermia induced by these amphetamines. Additionally, when neuroprotection was assayed with memantine (MEM), a dual antagonist of NMDA and alpha7 receptors, an effective neuroprotection was obtained also ahead of serotonergic injury induced by MDMA in rats. MEM also prevents MDMA effect on serotonin transporter functionality and METH effect on dopamine transporter (DAT), suggesting that behavioral effects of these psychostimulants can also be modulated by MEM. Finally, we have demonstrated that MEM prevents the impaired memory function induced by MDMA, and also, using binding studies with radioligands, we have characterized the interaction of these substances with nicotinic receptors. Studies at molecular level showed that both MDMA and METH displaced competitively the binding of radioligands with homomeric alpha7 and heteromeric nicotinic acetylcholine receptors (nAChRs), indicating that they can directly interact with them. In all the cases, MDMA displayed higher affinity than METH and it was higher for heteromeric than for alpha7 subtype. Pre-incubation of differentiated PC12 cells with MDMA or METH induces nAChR upregulation in a concentration- and time-dependent manner, as many nicotinic ligands do, supporting their functional interaction with nAChRs. Such interaction expands the pharmacological profile of amphetamines and can account for some of their effects.

Secretory vesicle rebound hyperacidification and increased quantal size resulting from prolonged methamphetamine exposure

Acute exposure to amphetamines (AMPHs) collapses secretory vesicle pH gradients, which increases cytosolic catecholamine levels while decreasing the quantal size of catecholamine release during fusion events. AMPH and methamphetamine (METH), however, are retained in tissues over long durations. We used optical and electron microscopic probes to measure the effects of long-term METH exposure on secretory vesicle pH, and amperometry and intracellular patch electrochemistry to observe the effects on neurosecretion and cytosolic catecholamines in cultured rat chromaffin cells. In contrast to acute METH effects, exposure to the drug for 6-48 h at 10 microM and higher concentrations produced a concentration-dependent rebound hyperacidification of secretory vesicles. At 5-10 microM levels, prolonged METH increased the quantal size and reinstated exocytotic catecholamine release, although very high (> 100 microM) levels of the drug, while continuing to produce rebound hyperacidification, did not increase quantal size. Secretory vesicle rebound hyperacidification was temperature dependent with optimal response at approximately 37 degrees C, was not blocked by the transcription inhibitor, puromycin, and appears to be a general compensatory response to prolonged exposure with membranophilic weak bases, including AMPHs, methylphenidate, cocaine, and ammonia. Thus, under some conditions of prolonged exposure, AMPHs and other weak bases can enhance, rather than deplete, the vesicular release of catecholamines via a compensatory response resulting in vesicle acidification.

Mitochondrial stress-induced dopamine efflux and neuronal damage by malonate involves the dopamine transporter

Endogenous striatal dopamine (DA) overflow has been associated with neuropathological conditions resulting from ischemia, psychostimulants, and metabolic inhibition. Malonate, a reversible inhibitor of succinate dehydrogenase, models the effects of energy impairment in neurodegenerative disorders. We have previously reported that the striatal DA efflux and damage to DA nerve terminals resulting from intrastriatal malonate infusions is prevented by prior DA depletion, suggesting that DA plays a role in the neuronal damage. We presently report that the malonate-induced DA efflux is partially mediated by reverse transport of DA from the cytosol to the extracellular space via the DA transporter (DAT). Pharmacological blockade of the DAT with a series of structurally different inhibitors [cocaine, mazindol, 1-(2-(bis(4-fluophenyl methoxy) ethyl)-4-(3-(4-fluorophenyl)-propyl)piperazine) dimethane sulfonate (GBR 13098) and methyl(-)-3beta-(p-fluorophenyl)-1alphaH,5alphaH-tropane-2beta-carboxylate1,5-naphthalene (Win 35,428)] attenuated malonate-induced DA overflow in vivo and protected mice against subsequent damage to DA nerve terminals. Consistent with these findings, the DAT inhibitors prevented malonate-induced damage to DA neurons in mesencephalic cultures and also protected against the loss of GABA neurons in this system. The DAT inhibitors did not modify malonate-induced formation of reactive oxygen species or lactate production, indicating that the DAT inhibitors neither exert antioxidant effects nor interfere with the actions of malonate. Taken together, these findings provide direct evidence that mitochondrial impairment and metabolic stress cause striatal DA efflux via the DAT and suggest that disruptions in DA homeostasis resulting from energy impairment may contribute to the pathogenesis of neurodegenerative diseases.

Cocaine abusers have an overexpression of alpha-synuclein in dopamine neurons

Alpha-synuclein is a presynaptic protein that has been implicated as a possible causative agent in the pathogenesis of Parkinson's disease. The native protein is a major component of nigral Lewy bodies in Parkinson's disease, and full-length alpha-synuclein accumulates in Lewy neurites. Here we present evidence that alpha-synuclein levels are elevated in midbrain dopamine (DA) neurons of chronic cocaine abusers. Western blot and immunoautoradiographic studies were conducted on postmortem neuropathological specimens from cocaine users and age-matched drug-free control subjects. The results demonstrated that alpha-synuclein levels in the DA cell groups of the substantia nigra/ventral tegmental complex were elevated threefold in chronic cocaine users compared with normal age-matched subjects. The increased protein levels in chronic cocaine users were accompanied by changes in the expression of alpha-synuclein mRNA in the substantia nigra and ventral tegmental area. Although alpha-synuclein expression is prominent in the hippocampus, there was no increase in protein expression in this brain region. The levels of beta-synuclein, a possible negative regulator of alpha-synuclein, also were not affected by cocaine exposure. Alpha-synuclein protein levels were increased in the ventral tegmental area, but not the substantia nigra, in victims of excited cocaine delirium who experienced paranoia, marked agitation, and hyperthermia before death. The overexpression of alpha-synuclein may occur as a protective response to changes in DA turnover and increased oxidative stress resulting from cocaine abuse. However, the accumulation of alpha-synuclein protein with long-term cocaine abuse may put addicts at increased risk for developing the motor abnormalities of Parkinson's disease.

Effect of temperature on dopamine transporter function and intracellular accumulation of methamphetamine: implications for methamphetamine-induced dopaminergic neurotoxicity

Hyperthermia exacerbates and hypothermia attenuates methamphetamine (METH)-induced dopamine (DA) neurotoxicity. The mechanisms underlying these temperature effects are unknown. Given the essential role of the DA transporter (DAT) in the expression of METH-induced DA neurotoxicity, we hypothesized that the effect of temperature on METH-induced DA neurotoxicity is mediated, at least in part, at the level of the DAT. To test this hypothesis, the effects of small, physiologically relevant temperature changes on DAT function were evaluated in two types of cultured neuronal cells: (1) a neuroblastoma cell line stably transfected with human DAT cDNA and (2) rat embryonic mesencephalic primary cells that naturally express the DAT. Temperatures for studies of DAT function were selected based on core temperature measurements in animals exposed to METH under usual ambient (22 degrees C) and hypothermic (6 degrees C) temperature conditions, where METH neurotoxicity was fully expressed and blocked, respectively. DAT function, determined by measuring accumulation of radiolabeled DA and 1-methyl-4-phenylpyridinium (MPP(+)), was found to directly correlate with temperature, with higher levels of substrate uptake at 40 degrees C, intermediate levels at 37 degrees C, and lower levels at 34 degrees C. DAT-mediated accumulation of METH also directly correlated with temperature, with greater accumulation at higher temperatures. These findings indicate that relatively small, physiologically relevant changes in temperature significantly alter DAT function and intracellular METH accumulation, and suggest that the effect of temperature on METH-induced DA neurotoxicity is mediated, at least in part, at the level of the DAT.

Choreoathetoid movements in cocaine dependence

BACKGROUND

To evaluate the severity of choreoathetoid movements in cocaine dependent (CD) subjects and age-matched normal control subjects.

METHODS

Choreoathetoid movements were evaluated using the Abnormal Involuntary Movement Scale (AIMS) in samples of 71 CD, 56 normal control, and 9 amphetamine-dependent male subjects.

RESULTS

The CD subjects had a significantly increased nonfacial (limbs plus body) AIMS subscore. When the nonfacial AIMS scores of the two groups were compared in relation to age, a significant age by diagnosis interaction was observed, indicating that the differences between groups were most marked in the younger age groups. The facial AIMS scores were also increased but only in the youngest CD cohort (under 32 years of age). The comparison group of 9 younger amphetamine-dependent subjects also showed increased AIMS scores.

CONCLUSIONS

Increases in choreoathetoid movements in younger cocaine and amphetamine-dependent subjects may be related to their psychostimulant use. The absence of differences in choreoathetoid movements between the older CD subjects and normal control subjects may represent an age-related self-selection effect.

Effects of antipsychotics, vitamin E, and MK-801 on dopamine dynamics in the rat brain following discontinuation of cocaine

Cocaine, 10 mg/kg, I.P., twice daily, was given to rats for 1 week. At 1 and 4 weeks following discontinuation of cocaine, the initial rate of 3,4-dihydroxyphenylacetic acid (DOPAC) formation was assessed. The initial rate of DOPAC formation was found to be decreased in the frontal and cingulate cortices at 1 week, but was only decreased in the frontal cortex at 4 weeks. When administered in conjunction with cocaine, haloperidol, clozapine, and vitamin E, but not MK-801, were found to prevent cocaine's effects. In addition to the potential value these findings have for further understanding cocaine abuse, it is proposed that the alteration in dopamine metabolism produced by cocaine, and the ability of haloperidol, clozapine and vitamin E to decrease cocaine's effects, model some biochemical aspects of schizophrenia.

Free radicals and the pathobiology of brain dopamine systems

Oxygen is an essential element for normal life. However, reactive oxygen species (ROS) can also participate in deleterious reactions that can affect lipid, protein, and nucleic acid. Normal physiological function thus depends on a balance between these ROS and the scavenging systems that aerobic organisms have developed over millennia. Tilting of that balance towards a pro-oxidant state might result from both endogenous and exogenous causes. In the present paper, we elaborate on the thesis that the neurodegenerative effects of two drugs, namely methamphetamine (METH, ICE) and methylenedioxymethamphetamine (MDMA, Ecstasy) are due to ROS overproduction in monoaminergic systems in the brain. We also discuss the role of oxygen-based species in 6-hydroxydopamine (6-OHDA)-induced nigrostriatal dopaminergic degeneration and in Parkinson's disease. Studies are underway to identify specific cellular and molecular mechanisms that are regulated by oxygen species. These studies promise to further clarify the role of oxidative stress in neurodegeneration and in plastic changes that occur during the administration of addictive agents that affect the brain.

Methamphetamine-induced alterations in dopamine transporter function

Repeated methamphetamine (METH) administration has been shown to produce differing neurochemical as well as behavioral effects in rats. This study was designed to examine the effects of acute and chronic METH exposure on uptake and release of [3H]dopamine (DA) in cultured midbrain dopamine neurons to determine if persistent neuronal adaptations ensue. In addition, we have assessed DA D2 receptor function to determine if chronic METH alters this receptor. Fetal midbrain cultures were exposed to METH (1, 10 microM) for 5 days and dopaminergic function examined 1 or 7 days after drug removal. The ability of METH to release [3H]DA was compared to other releasing agents as well as several potent uptake inhibitors. Chronic exposure to a release-promoting concentration of METH resulted in either no change or a reduction in [3H]DA release upon subsequent METH challenge. Pretreatment with METH was also found to cause a decrease in the Bmax for [3H]raclopride binding, suggesting that persistently elevated DA levels cause a downregulation of DA D2 receptors. Examination of transporter kinetics utilizing initial velocity of uptake revealed that METH treatment caused a significant decrease in affinity (K(m)) for the substrate (DA), while not altering the maximal velocity of uptake (Vmax). Binding studies with [125I]RTI-55 revealed that there was no alteration in either the Bmax or Kd for this ligand, suggesting that the changes induced by METH treatment are due to alterations in K(m) and not in the number of DA transport sites. The results from these studies indicate that METH treatment produces a modification in transporter function which may be associated with both the altered uptake and release of [3H]DA. These changes have broad implications for the regulation of transporter activity not only because of the relevance to pre-synaptic mechanisms controlling neurotransmission, but also to the importance of the neuronal adaptation that occurs in response to chronic METH exposure.

Species differences in the role of excitatory amino acids in experimental parkinsonism

The present review discusses species differences in relation to the effects produced by the neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP); in particular, it focuses on recent evidence regarding the role of excitatory amino acids in experimental parkinsonism. The main aim of the review is to provide a phylogenetic perspective which may serve as a useful tool to study Parkinson's disease in rodents. Excitotoxicity might represent the final common pathway on which the actions of different neurotoxins, selectively directed towards nigrostriatal dompaminergic neurons, converge. This is clearly demonstrated in methamphetamine- and 6-dihydroxy-dopamine-induced parkinsonism. The role of excitotoxicity in the mechanism of action of MPTP is less clear. Although there are several species differences for MPTP it is possible to obtain in mice the same effects induced in MPTP-treated primates by combining acetaldehyde or diethyldithiocarbamate with MPTP administration. When mice are administered these combined treatments, the onset of experimental parkinsonism can be prevented using the same pharmacological agents (i.e. glutamate N-methyl-D-aspartate antagonists) that are effective in primates.

L-deprenyl fails to protect mesencephalic dopamine neurons and PC12 cells from the neurotoxic effect of 1-methyl-4-phenylpyridinium ion

L-Deprenyl, a monoamine oxidase (MAO)-B inhibitor, appears to slow down the progression of Parkinson's disease. While inhibition of MAO-B activity can account for some of the effects of this substance, the basis by which L-deprenyl slows the progression of the disease remains controversial. In recent years, a new mechanism of action has emerged that may explain the ability of L-deprenyl to increase neuronal survival. L-deprenyl has been reported to modify gene expression and protein synthesis in astrocytes and PC12 cells. In this study, we tested the ability of L-deprenyl to protect mouse mesencephalic cells from the toxicity of the 1-methyl-4-phenyl pyridinium ion (MPP+). We exposed mouse mesencephalic cell cultures to L-deprenyl (10 microM) and, 24 h later, to MPP+ (2.5 microM). On the fifth day after L-deprenyl and MPP+ exposition, cells were washed free of drugs, and the following day they were tested for dopamine uptake, intracellular dopamine content and tyrosine hydroxylase immunoreactivity. The experiments were performed either in the presence or in the absence of glia. It was found that L-deprenyl pretreatment failed to achieve any protection against MPP+ toxicity. The fall in dopamine uptake and intracellular dopamine content, and the diminution of tyrosine hydroxylase immunoreactivity observed in cells pretreated with L-deprenyl and then given MPP+ were not significantly different from the values observed in cells treated with MPP+ alone. Additional experiments performed in PC12 cells, confirmed the failure of L-deprenyl to abolish the toxicity of MPP+. Our data seem to be at variance with previous reports demonstrating that the MAO-B inhibitor L-deprenyl protects dopaminergic neurons against MPP+ toxicity [12,20]; furthermore they do not support alternative mechanisms of action of L-deprenyl against MPP+ toxicity.

Nitric oxide is a mediator of methamphetamine (METH)-induced neurotoxicity. In vitro evidence from primary cultures of mesencephalic cells

METH is a monoaminergic toxic that destroys dopamine terminals in vivo. Oxidative mechanisms associated with DA metabolism are thought to play an important role in its toxic effects. These ideas were supported by the demonstration that CuZn-superoxide dismutase (CuZnSOD) transgenic mice were protected against the toxic effects of the drug. In the present study, we sought to determine if nitric oxide (NO) production was also involved in METH-induced neurotoxicity using primary cultures obtained from fetal rat mesencephalon. METH caused dose- and time-dependent cell death in vitro. Blockade of nitric oxide (NO) formation with several nitric oxide (NO) synthase blockers attenuated METH-mediated toxicity. Moreover, inhibition of ADP-ribosylation with nicotinamide and benzamide also provided protection against the toxicity of the drug. These results, together with our previous results in transgenic mice, support a role for free radicals in METH-induced toxic effects.

The vesicular monoamine transporter, in contrast to the dopamine transporter, is not altered by chronic cocaine self-administration in the rat

Although much evidence suggests that the brain dopamine transporter (DAT) is susceptible to dopaminergic regulation, only limited information is available for the vesicular monoamine transporter (VMAT2). In the present investigation, we used a chronic, unlimited-access, cocaine self-administration paradigm to determine whether brain levels of VMAT2, as estimated using [3H]dihydrotetrabenazine (DTBZ) binding, are altered by chronic exposure to a dopamine uptake blocker. Previously, we showed that striatal and nucleus accumbens DAT levels, as estimated by [3H]WIN 35,428 and [3H]GBR 12,935 binding, are altered markedly using this animal model (Wilson et al., 1994). However, in sequential sections from the same animals, [3H]DTBZ binding was normal throughout the entire rostrocaudal extent of the basal ganglia (including striatum and nucleus accumbens), cerebral cortex, and diencephalon, as well as in midbrain and brainstem monoamine cell body regions, both on the last day of cocaine access and after 3 weeks of drug withdrawal. These data provide additional evidence that VMAT2, unlike DAT, is resistant to dopaminergic regulation.

HIV-1 gp120-induced neurotoxicity to midbrain dopamine cultures

HIV-1-associated cognitive/motor dysfunction is a frequent neurological complication of acquired immunodeficiency syndrome (AIDS) and has been termed AIDS dementia complex (ADC). The HIV-1 envelope glycoprotein gp120 has been implicated in producing brain injury associated with ADC. The purpose of the present study was to determine if gp120-induced neurotoxicity is associated with damage to dopaminergic systems. Exposure of rat midbrain dopamine cultures to gp120 for 3 days reduced the ability of dopaminergic cells to transport this amine and also resulted in a reduction in dopamine neuron process length while it did not alter either dopamine cell number or the total number of neuronal cells. These detrimental effects of gp120 were prevented by an NMDA receptor antagonist (MK-801) or by preincubation with anti-gp120 antibody. These results suggest that dopaminergic neuronal damage may contribute to the manifestations of AIDS dementia complex.

Influence of neurotrophic factors on morphine- and cocaine-induced biochemical changes in the mesolimbic dopamine system

Previous research has shown an increase in tyrosine hydroxylase in the ventral tegmental area following chronic morphine and chronic cocaine treatments. Chronic morphine treatment also increases levels of glial fibrillary acidic protein in this brain region. In the present study, we investigated the effects of infusing neurotropic factors (nerve growth factor, brain-derived neurotrophic factor, neurotrophin-3, neurotrophin-4 or ciliary neurotrophic factor) via midline intra-ventral tegmental area cannulae on these biochemical changes. Our studies examined the effects of neurotrophic factor infusion alone, neurotrophic factor infusion followed by morphine treatment, morphine treatment followed by neurotrophic factor infusion, and concurrent neurotrophic factor infusion and cocaine treatment. Brain-derived neurotrophic factor, which by itself tended to decrease tyrosine hydroxylase levels in the ventral tegmental area, prevented the characteristic increase in tyrosine hydroxylase following morphine and cocaine exposure and reversed the increase in rats pretreated with morphine. Neurotrophin-4 and neurotrophin-3 exerted similar effects. In addition, neurotrophin-4 prevented the morphine-induced increase in glial fibrillary acidic protein. In contrast, ciliary neurotrophic factor infusions alone resulted in an increase in tyrosine hydroxylase levels, with no additional increase induced by morphine or cocaine coadministration. Nerve growth factor alone had no effect on tyrosine hydroxylase or glial fibrillary acidic protein levels and did not affect morphine's ability to induce these proteins. We also looked at the effects of intra-ventral tegmental area infusion of neurotrophic factor on cAMP-dependent protein kinase and adenylyl cyclase activity in the nucleus accumbens, both of which are increased by chronic morphine or cocaine exposure. In general, regulation of cAMP-dependent protein kinase and adenylyl cyclase morphine by neurotrophic factors paralleled effects seen in the ventral tegmental area. Intra-ventral tegmental area infusion of brain-derived neurotrophic factor (or neurotrophin-4) alone tended to decrease cAMP-dependent protein kinase and adenylyl cyclase activity in the nucleus accumbens and prevented the morphine-induced increases in these enzymes. These effects were not seen with ciliary neurotrophic factor or nerve growth factor. These studies demonstrate novel interactions within the ventral tegmental area, and its target the nucleus accumbens, between neurotrophic factors and drugs of abuse, which have potentially important implications for the pathophysiology and treatment of drug addiction.

Role of excitatory amino-acids in diethyldithiocarbamate-induced cell death in mesencephalic cultures

The effects of diethyldithiocarbamate (DDC) and DDC plus glutamate on mesencephalic cell cultures were investigated. DDC 10 microM was toxic for cell cultures as assessed by observation under a phase-contrast microscope and the drop in [3H]dopamine uptake. Moreover, DDC 1 microM greatly potentiated cell death induced by glutamate 10 and 50 microM. (+)MK801, a selective non-competitive antagonist of NMDA receptors, completely prevented the toxicity of the two neurotoxins.

Sex difference in sensitization to the locomotor effects of mazindol in rats

Male and female rats were treated daily for 7 days with mazindol (5, 10, and 20 mg/kg), an anorectic drug, and tested in the open field. Mazindol developed sensitization to its locomotor stimulatory effect in both sexes on day 7 with a nondose-dependent pattern of response. However, the locomotor activity appeared to be sex dependent, female rats being more sensitive. Following a challenge dose of mazindol (10 and 20 mg/kg) on day 10, a marked enhancement of locomotion was seen in female rats. These findings indicate that repeated administration of mazindol produces sex-dependent sensitization to its effect on locomotor behavior.

Long-term cocaine administration is not neurotoxic to cultured fetal mesencephalic dopamine neurons

The psychostimulants cocaine and methamphetamine produce their euphoric effects through an interaction with the mesolimbic dopamine system. Methamphetamine, unlike cocaine, has been shown to be neurotoxic to both dopaminergic and serotonergic systems. We have previously determined that a 6 day exposure to methamphetamine causes neuronal damage to tyrosine hydroxylase-immunopositive cells in our tissue culture model of the mesencephalon. Over the same exposure period, cocaine neither impaired neuronal function nor altered dopamine cell survival. To test whether a longer exposure period to cocaine would alter dopamine function, we added cocaine (100 microM) to the cultures once daily for either 8 or 11 days and examined changes in dopamine uptake, cell survival and morphology 24 h after the last administration. Cocaine did not produce any signs of neurotoxicity in the mesencephalic cultures.