Amphetamine-induced neurite injury in PC12 cells through inhibiting GAP-43 pathway.

Amphetamine (AMPH) causes the degeneration of dopamine terminals in the central nervous system. The mechanisms for this damage are unclear. We found AMPH reduced level of GAP-43 in the striatum of rats that receives rich dopaminergic terminals. Using PC12 cells as dopaminergic neuronal models, we further found that AMPH inhibited GAP-43 and GAP-43 phosphorylation in PC12 cells. The reduced GAP-43 was correlated with neurite injury of PC12 cells. The PKCß1, an upstream molecule of GAP-43, was also inhibited by AMPH. Phorbol 12-myristate 13-acetate (PMA) as a specific activator of PKC increased levels of PKCß1 and GAP-43, and efficiently prevented neurite degeneration of PC12 cells induced by AMPH. On the other side, enzastuarin, an inhibitor of PKC, decreased levels of PKCß1 and GAP-43, and caused neurite injury of PC12 cells. Together, our results suggest that AMPH induces neurite injury in PC12 cells through inhibiting PKCß1/GAP-43 pathway.

Para-Halogenation of Amphetamine and Methcathinone Increases the Mitochondrial Toxicity in Undifferentiated and Differentiated SH-SY5Y Cells.

Halogenation of amphetamines and methcathinones has become a common method to obtain novel psychoactive substances (NPS) also called "legal highs". The para-halogenated derivatives of amphetamine and methcathinone are available over the internet and have entered the illicit drug market but studies on their potential neurotoxic effects are rare. The primary aim of this study was to explore the neurotoxicity of amphetamine, methcathinone and their para-halogenated derivatives 4-fluoroamphetamine (4-FA), 4-chloroamphetamine (PCA), 4-fluoromethcathinone (4-FMC), and 4-chloromethcathinone (4-CMC) in undifferentiated and differentiated SH-SY5Y cells. We found that 4-FA, PCA, and 4-CMC were cytotoxic (decrease in cellular ATP and plasma membrane damage) for both cell types, whereby differentiated cells were less sensitive. IC50 values for cellular ATP depletion were in the range of 1.4 mM for 4-FA, 0.4 mM for PCA and 1.4 mM for 4-CMC. The rank of cytotoxicity observed for the para-substituents was chloride > fluoride > hydrogen for both amphetamines and cathinones. Each of 4-FA, PCA and 4-CMC decreased the mitochondrial membrane potential in both cell types, and PCA and 4-CMC impaired the function of the electron transport chain of mitochondria in SH-SY5Y cells. 4-FA, PCA, and 4-CMC increased the ROS level and PCA and 4-CMC induced apoptosis by the endogenous pathway. In conclusion, para-halogenation of amphetamine and methcathinone increases their neurotoxic properties due to the impairment of mitochondrial function and induction of apoptosis. Although the cytotoxic concentrations were higher than those needed for pharmacological activity, the current findings may be important regarding the uncontrolled recreational use of these compounds.

ITGB4 deficiency in bronchial epithelial cells directs airway inflammation and bipolar disorder-related behavior.

BACKGROUND: Chronic persistent airway inflammation has been associated with the comorbidity of asthma and bipolar disorder (BD). However, the direct relevance between airway inflammation and BD-like psychiatric comorbidity is almost unknown. Integrin ß4 (ITGB4) is downregulated on the airway epithelial of asthma patients, which might play a critical role in the parthenogenesis of airway inflammation. So this study aimed to examine the role of ITGB4 deficiency in mediating airway inflammation and further leading to the BD-like behaviors. METHODS: ITGB4-/- mice were generated by mating ITGB4fl/fl mice with CCSP-rtTAtg/-/TetO-Cretg/tg mice. Mania-like behavior tests were performed, including hyperlocomotion, D-amphetamine-induced hyperactivity, open-field test, and elevated plus-maze test. Depressive-like behavior tests were carried out, including sucrose preference, forced swimming, and learned helplessness. Inflammatory cells (Th17, Th1, Th2) in the lung were examined by flow cytometry. Futhermore, inflammatory cytokines (IL-4, IL-13) in bronchoalveolar lavage fluid and sera were detected by ELISA. Protein expression of the IL-4Rα on choroid plexus, microglial marker (IBA1), and synapse-associated proteins (synaptophysin, SYP) in the hippocampus and prefrontal cortex were examined by western blotting. Additionally, proinflammatory cytokines (IL-1ß, IL-6, and TNF-α) in the hippocampus and prefrontal cortex were detected by immunohistochemistry. Inflammatory disorder in the lung, hippocampus, and prefrontal cortex was tested by hematoxylin and eosin (H&E) staining. And cell apoptosis in the hippocampus and prefrontal cortex was measured by TUNEL test. RESULTS: ITGB4-/- mice exhibited mania-like behavior, including hyperlocomotion, D-amphetamine-induced hyperactivity, and reduced anxiety-like behavior. While under stressful conditions, ITGB4-/- mice manifested depressive-like behavior, including anhedonia, behavioral despair, and enhanced learned helplessness. At the same time, ITGB4-/- mice mainly exerted Th2-type inflammation in periphery, like the number and major cytokines IL-4 and IL-13 of Th2-type inflammation. ITGB4-/- mice also showed a significant increase of microglia and pro-inflammatory cytokines such as IL-1ß, IL-6, and TNF-α in the hippocampus and prefrontal cortex. Additionally, neuron damage, increased neuron apoptosis, and the decrease of SYP were found in ITGB4-/- mice. CONCLUSIONS: These findings confirmed that airway inflammatory induced by ITGB4 deficiency is the important incentive for the BD-like behavior during asthma pathogenesis. The ITGB4-deficient mice provide a validated animal model for us to study the possible mechanism of BD-like psychiatric comorbidity of asthma patients.

Amphetamine Neurotoxicity in PC12 Cells through the PP2A/AKT/GSK3ß Pathway.

Amphetamine (AMPH) abuse can influence neuropsychiatric disorders and cell apoptosis by interfering with the protein kinase B/ glycogen synthase kinase 3 beta (AKT/GSK3ß) pathway. However, the mechanisms underlying this regulation are poorly understood. Using PC12 cells, we found that AMPH inhibited AKT and GSK-3ß phosphorylation levels and increased total GSK-3ß levels. Furthermore, AMPH caused an increase in the activity of protein phosphatase 2 (PP2A), a signaling protein upstream of AKT, which in turn inhibited phosphorylated AKT levels. Okadaic acid, a PP2A inhibitor, protected PC12 cells against AMPH-induced apoptosis. Together, our results suggest that the PP2A/AKT/GSK3ß pathway plays an important role in AMPH-induced neurotoxicity.

Toxicity of the amphetamine metabolites 4-hydroxyamphetamine and 4-hydroxynorephedrine in human dopaminergic differentiated SH-SY5Y cells.

Amphetamine (AMPH) is a psychostimulant used worldwide by millions of patients in the clinical treatment of attention deficit hyperactivity disorder, narcolepsy or even obesity, and is also a drug of abuse. 4-Hydroxynorephedrine (4-OHNE) and 4-hydroxyamphetamine (4-OHAMPH) are two major metabolites known to persist in the brain longer than AMPH. The contribution of AMPH metabolites for its neurotoxicity is undetermined. We evaluated the toxicity of AMPH and its metabolites 4-OHNE and 4-OHAMPH, obtained by chemical synthesis, in human dopaminergic differentiated SH-SY5Y neurons. Cells were exposed to AMPH (concentration range 0-5mM) or 4-OHAMPH or 4-OHNE (concentration range 0-10mM) for 24 or 48h, and the viability was determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) and lactate dehydrogenase (LDH) leakage assays. Results showed that for both AMPH and the metabolites a concentration-dependent toxicity was observed. The toxic concentration 50% (TC50) for AMPH and 4-OHNE following 24h exposure was circa 3.5mM and 8mM, respectively. For 4-OHAMPH the TC50 was not reached in the tested concentration range. N-acetyl cysteine, cycloheximide, l-carnitine, and methylphenidate were able to reduce cell death induced by AMPH TC50. Acridine orange/ethidium bromide staining showed evident signs of late apoptotic cells and necrotic cells following 24h exposure to AMPH 3.50mM. The 4-OHAMPH metabolite at 8.00mM originated few late apoptotic cells, whereas 4-OHNE at 8.00mM resulted in late apoptotic cells and necrotic cells, in a scenario similar to AMPH. In conclusion, the AMPH metabolite 4-OHNE is more toxic than 4-OHAMPH, nonetheless both are less toxic than the parent compound in vitro. The most toxic metabolite 4-OHNE has longer permanence in the brain, rendering likely its contribution for AMPH neurotoxicity.

Amphetamine in adolescence disrupts the development of medial prefrontal cortex dopamine connectivity in a DCC-dependent manner.

Initiation of drug use during adolescence is a strong predictor of both the incidence and severity of addiction throughout the lifetime. Intriguingly, adolescence is a period of dynamic refinement in the organization of neuronal connectivity, in particular medial prefrontal cortex (mPFC) dopamine circuitry. The guidance cue receptor, DCC (deleted in colorectal cancer), is highly expressed by dopamine neurons and orchestrates their innervation to the mPFC during adolescence. Furthermore, we have shown that amphetamine in adolescence regulates DCC expression in dopamine neurons. Drugs in adolescence may therefore induce their enduring behavioral effects via DCC-mediated disruption in mPFC dopamine development. In this study, we investigated the impact of repeated exposure to amphetamine during adolescence on both the development of mPFC dopamine connectivity and on salience attribution to drug context in adulthood. We compare these effects to those induced by adult exposure to an identical amphetamine regimen. Finally, we determine whether DCC signaling within dopamine neurons is necessary for these events. Exposure to amphetamine in adolescence, but not in adulthood, leads to an increase in the span of dopamine innervation to the mPFC, but a reduction of presynaptic sites present on these axons. Amphetamine treatment in adolescence, but not in adulthood, also produces an increase in salience attribution to a previously drug-paired context in adulthood. Remarkably, DCC signaling within dopamine neurons is required for both of these effects. Drugs of abuse in adolescence may therefore induce their detrimental behavioral consequences by disrupting mesocortical dopamine development through alterations in the DCC signaling cascade.

MRI reveals differential effects of amphetamine exposure on neuroglia in vivo.

How amphetamine affects the neuroglia in living brains is not well understood. In an effort to elucidate this effect, we investigated neuroglia in response to amphetamine exposure using antisense (AS) or sense (S) phosphorothioate-modified oligodeoxynucleotide (sODN) sequences that correspond to glial fibrillary acidic protein (GFAP) mRNA (AS-gfap or S-gfap, respectively) expression. The control is a random-sequence sODN (Ran). Using cyanine 5.5-superparamagnetic iron oxide nanoparticle (Cy5.5-SPION) labeling and fluorescent microscopy, we demonstrated that living neural progenitor cells (PC-12.1), as well as the cells in fresh brain slices and intact brains of male C57BL6 mice, exhibited universal uptake of all of the sODNs but rapidly excluded all sODN-Ran and most S-gfap. Moreover, transmission electron microscopy revealed electron-dense nanoparticles only in the neuroglia of normal or transgenic mice [B6;DBA-Tg(Fos-tTA, Fos-EGFP*)1MmayTg(tetO-lacZ,tTA*)1Mmay/J] that had been administered AS-gfap or Cy5.5-SPION-gfap. Subtraction R2* maps from mice with acute and chronic amphetamine exposure demonstrated, validated by postmortem immunohistochemistry, a reduction in striatal neuroglia, with gliogenesis in the subventricular zone and the somatosensory cortex in vivo. The sensitivity of our unique gene transcript targeted MRI was illustrated by a positive linear correlation (r(2)=1.0) between in vivo MRI signal changes and GFAP mRNA copy numbers determined by ex vivo quantitative RT-PCR. The study provides direct evidence for targeting neuroglia by antisense DNA-based SPION-gfap that enables in vivo MRI of inaccessible tissue with PCR sensitivity. The results enable us to conclude that amphetamine induces toxicity to neuroglia in vivo, which may cause remodeling or reconnectivity of neuroglia.

The neurotrophic factor pleiotrophin modulates amphetamine-seeking behaviour and amphetamine-induced neurotoxic effects: evidence from pleiotrophin knockout mice.

Pleiotrophin (PTN), a neurotrophic factor with important roles in survival and differentiation of dopaminergic neurons, is up-regulated in the nucleus accumbens after amphetamine administration suggesting that PTN could modulate amphetamine-induced pharmacological or neuroadaptative effects. To test this hypothesis, we have studied the effects of amphetamine administration in PTN genetically deficient (PTN -/-) and wild type (WT, +/+) mice. In conditioning studies, we found that amphetamine induces conditioned place preference in both PTN -/- and WT (+/+) mice. When these mice were re-evaluated after a 5-day period without amphetamine administration, we found that WT (+/+) mice did not exhibit amphetamine-seeking behaviour, whereas, PTN -/- mice still showed a robust drug-seeking behaviour. In immunohystochemistry studies, we found that amphetamine (10 mg/kg, four times, every 2 hours) causes a significant increase of glial fibrillary acidic protein positive cells in the striatum of amphetamine-treated PTN -/- mice compared with WT mice 4 days after last administration of the drug, suggesting an enhanced amphetamine-induced astrocytosis in the absence of endogenous PTN. Interestingly, we found in concomitant in vitro studies that PTN (3 µM) limits amphetamine (1 mM)-induced loss of viability of PC12 cell cultures, effect that could be related to the ability of PTN to induce the phosphorylation of Akt and ERK1/2. To test this possibility, we used specific Akt and ERK1/2 inhibitors uncovering for the first time that PTN-induced protective effects against amphetamine-induced toxicity in PC12 cells are mediated by the ERK1/2 signalling pathway. The data suggest an important role of PTN to limit amphetamine-induced neurotoxic and rewarding effects.

Prefrontal inositol triphosphate is molecular correlate of working memory in nonhuman primates.

Working memory (WM) is a process of actively maintaining information in the mind for a relatively short period of time, and prefrontal cortex (PFC) has been thought to play a central role in its function. However, our understanding of underlying molecular events that translate into WM behavior remains elusive. To shed light on this issue, we have used three distinct nonhuman primate models of WM where each model represents three WM conditions: normal control, WM-deficient, and recuperated to normal from WM deficiency. Based on the hypothesis that there is a common molecular substrate for the coding of WM behavior, we have studied the relationship of these animals' performance on a WM task with their PFC levels of molecular components associated with Gq-phospholipase C and cAMP pathways, with the idea of identifying the footprints of such biomolecules. We observed that in all of the primate models WM deficiency was strongly related to the reduced concentration of IP(3) in PFC, whereas recuperation of WM-deficient animals to normal condition was associated with the normalization in IP(3) level. However, this correlation was absent or weak for cAMP, active protein kinase A, dopamine D(1) receptor, and Gq protein. In addition, WM deficiency related not only to pharmacological conditions but also to aging. Thus, it is suggested that optimal IP(3) activity is essential for normal WM function and the maintenance of intracellular IP(3)-mediated Ca(2+) level in PFC may serve as biochemical substrate for the expression of WM behavior.

Priming for L-DOPA-induced abnormal involuntary movements increases the severity of amphetamine-induced dyskinesia in grafted rats.

In some patients, graft-induced dyskinesia develops following intrastriatal transplantation of embryonic neural tissue for the treatment of Parkinson's disease. The mechanisms underlying these involuntary movements need to be clarified before this approach to clinical cell therapy can be developed further. We previously found that rats with 6-OHDA lesions, primed with L-DOPA treatment and that have subsequently undergone intrastriatal graft surgery exhibit involuntary movements when subjected to amphetamine. This model of amphetamine-induced AIMs reflects a pattern of post-graft behaviours that in the absence of robust spontaneous GID in the rat is the closest approximation that we currently have available. We now show that they are associated with the chronic administration of L-DOPA prior to the transplantation surgery. We also demonstrate that neither changes in c-fos nor FosB/DeltaFosB expression in the lateral striatum are associated with the expression of these behaviours. Taken together, these data reveal that the severity of abnormal movements elicited by amphetamine in grafted animals may relate to previous L-DOPA exposure and dyskinesia development, but they develop through mechanisms that are independent of FosB/DeltaFosB upregulation.

Prenatal exposure to drugs: effects on brain development and implications for policy and education.

The effects of prenatal exposure to drugs on brain development are complex and are modulated by the timing, dose and route of drug exposure. It is difficult to assess these effects in clinical cohorts as these are beset with problems such as multiple exposures and difficulties in documenting use patterns. This can lead to misinterpretation of research findings by the general public, the media and policy makers, who may mistakenly assume that the legal status of a drug correlates with its biological impact on fetal brain development and long-term clinical outcomes. It is important to close the gap between what science tells us about the impact of prenatal drug exposure on the fetus and the mother and what we do programmatically with regard to at-risk populations.

Recreational amphetamine use and risk of HIV-related non-Hodgkin lymphoma.

The results of many laboratory studies suggest that amphetamine use may lead to altered immune function and cytokine expression, both of which are implicated in HIV-related lymphomagenesis. We examined the hypothesis that use of amphetamines modifies risk of non-Hodgkin lymphoma (NHL) in HIV-infected men in the Multicenter AIDS Cohort Study. Data on amphetamine use were collected every six months during the follow-up period between 1984 and 2002. A total of 171 NHL cases were diagnosed from the 19,250 person-years accrued. Multivariable Cox models were used to estimate the effects of baseline exposures, time-varying recent exposures, and three years lagged exposures on risk of NHL adjusting for potential confounders such as demographics, use of other substances, and risky sexual behaviors. We found that weekly or more frequent use of amphetamines was associated with an increased risk of NHL, with hazard ratios of 1.75 (95% CI = 0.81-3.77) for use at baseline, 4.73 (1.41-15.81) for recent use, and 3.05 (1.19-7.82) for three years prior use. Similar associations were observed when we separately examined systemic NHL and diffuse large B-cell lymphoma. Given these observations, the impact of amphetamines on lymphomagenesis among HIV-infected populations should be assessed more thoroughly.

Evaluation of glycosaminoglycans content and 5-hydroxytryptamine 2B receptor in the heart valves of Sprague-Dawley rats with spontaneous mitral valvulopathy--a possible exacerbation by dl-amphetamine sulfate in Fischer 344 rats?

Spontaneous valvulopathy has been described as nodular or segmental thickenings composed of fibromyxoid tissue in the subendocardium of various valve-leaflets in aging rats, but its pathogenesis and significance are incompletely understood. In this study, we examined the 5-hydroxytryptamine 2B receptor (5HT2BR) expression and characterization of extracellular matrix (ECM) components, and related these to the presence of valvulopathy in the mitral valve-leaflet (spontaneous mitral valvulopathy, SMV) of Sprague-Dawley (SD) rats. We also examined hearts from Fischer 344 (F344) rats treated with dl-amphetamine sulfate for 103 weeks to further explore the potential for drug-induced exacerbation of SMV. In SD rats, valve-leaflets with SMV exhibited a greater valve thickness, a higher amount of glycosaminoglycans, a lower amount of collagen and increased number of 5HT2BR-positive cells. Our data on morphology and ECM changes showed a striking similarity between SMV in SD rats and anorexigen-associated valvulopathy in humans, and increased 5HT2BR-positive cells in SMV implies that 5HT2BR may play a role in pathogenesis. Further, increased incidence and severity of SMV in F344 rats by treatment with dl-amphetamine suggest that a drug-induced exacerbation of SMV may exist in rats. However, additional research is needed to confirm a role for 5HT2BR in the pathogenesis of SMV in SD rats, and to further characterize the relationship between dl-amphetamine treatment and exacerbation of SMV in F344 rats.

Mitochondrial dysfunction and caspase activation in rat cortical neurons treated with cocaine or amphetamine.

Drug abuse is associated with brain dysfunction and neurodegeneration, and various recreational drugs induce apoptotic cell death. This study examined the role of the mitochondrial apoptotic pathway in psychostimulant-induced neuronal dysfunction. Using primary neuronal cultures, we observed that amphetamine (IC50=1.40 mM) was more potent than cocaine (IC50=4.30 mM) in inducing cell toxicity. Apoptotic cell death was further evaluated using cocaine and amphetamine concentrations that moderately decreased cell reduction capacity but did not affect plasma membrane integrity. Compared to cocaine, amphetamine highly decreased the mitochondrial membrane potential, as determined using the fluorescent probe rhodamine-123, whereas both drugs decreased mitochondrial cytochrome c. In contrast to amphetamine, cocaine cytotoxicity was partly mediated through effects on the electron transport chain, since cocaine toxicity was ameliorated in mitochondrial DNA-depleted cells lacking mitochondrially encoded electron transport chain subunits. Cocaine and amphetamine induced activation of caspases-2, -3 and -9 but did not affect activity of caspases-6 or -8. In addition, amphetamine, but not cocaine, was associated with the appearance of evident nuclear apoptotic morphology. These events were not accompanied by differences in the release of the apoptosis-inducing factor (AIF) from mitochondria. Our results demonstrate that although both amphetamine and cocaine activate the mitochondrial apoptotic pathway in cortical neurons, amphetamine is more likely to promote apoptosis.

Transplantation of human neural precursor cells in the 6-OHDA lesioned rats: effect of immunosuppression with cyclosporine A.

Neural precursor cells (NPC) may provide a source for restaurative therapy. We wanted to study the immunogenic potential of human NPC. We transplanted human NPCs with or without cyclosporine A (10 mg/kg) expanded in serum-free conditions into the striatum of rats unilaterally lesioned with 6-hydroxydopamine. Four months after transplantation, there was significant improvement of amphetamine-induced rotational behavior 9 non-immunosuppressed (13.1+/-4.9 pre vs 8.5+/-4.0 after grafting) but nor for 11 animals immunosuppressed with CyA (12.3+/-1.7 vs 11.3+/-2.8). The number of TH-IR cells was comparable in both groups (1,580+/-700 vs 1,274+/-295). All grafted animals only showed mild activation of astrocytes and macrophages within the graft. There was no evidence for tumor formation. Immunosuppression of rats, xenotransplanted with human NPC did not improve graft survival or function.

Differential cytotoxic responses of PC12 cells chronically exposed to psychostimulants or to hydrogen peroxide.

Repeated abuse of stimulant drugs, cocaine and amphetamine, is associated with extraneuronal dopamine accumulation in specific brain areas. Dopamine may be cytotoxic through the generation of reactive oxygen species, namely hydrogen peroxide (H2O2), resulting from dopamine oxidative metabolism. In this work, we studied the cytotoxicity in PC12 cells (a dopaminergic neuronal model) chronically and/or acutely exposed to cocaine or amphetamine, as compared to H2O2 exposure. Chronic cocaine treatment induced sensitization to acute cocaine insult and increased cocaine-evoked accumulation of extracellular dopamine, although no changes in dihydroxyphenylacetic acid (DOPAC) levels were observed. Moreover, dopamine was depleted in cells chronically exposed to amphetamine and acute amphetamine toxicity persisted in these cells, indicating that dopamine was not involved in amphetamine cytotoxicity. PC12 cells chronically treated with H2O2 were totally resistant to acute H2O2, but not to acute cocaine or amphetamine exposure, suggesting that the toxicity induced by these stimulant drugs is unrelated to adaptation to oxidative stress. Interestingly, chronic cocaine treatment largely, but not completely, protected the cells against a H2O2 challenge, whilst a decrement in intracellular ATP was observed. This study shows that chronic treatment of PC12 cells with cocaine or H2O2 modifies the cytotoxic response to an acute exposure to these agents.

Monoaminergic dysregulation in glutathione-deficient mice: possible relevance to schizophrenia?

Several lines of research have implicated glutathione (GSH) in schizophrenia. For instance, GSH deficiency has been reported in the prefrontal cortex of schizophrenics in vivo. Further, in rats postnatal GSH-deficiency combined with hyperdopaminergia led to cognitive impairments in the adult. In the present report we studied the effects of 2-day GSH-deficiency with L-buthionine-(S,R)-sulfoximine on monoaminergic function in mice. The effect of GSH-deficiency per se and when combined with the amphetamine and phencyclidine (PCP) models of schizophrenia was investigated. GSH-deficiency significantly altered tissue levels of dopamine (DA), 5-hydroxytryptamine (5-HT) and their respective metabolites homovanillic acid (HVA), and 5-hydroxyindoleacetic acid (5-HIAA) in a region-specific fashion. The effects of GSH-deficiency on tissue monoamines were distinct from and, generally, did not interact with the effects of amphetamine (5 mg/kg; i.p.) on tissue monoamines. Microdialysis studies showed that extracellular DA-release after amphetamine (5 mg/kg, i.p.) was two-fold increased in the nucleus accumbens of GSH-deficient mice as compared with control mice. Basal DA was unaltered. Further, extracellular levels of HVA in the frontal cortex and hippocampus and 5-HIAA in the nucleus accumbens were elevated by GSH-deficiency per se. Spontaneous locomotor activity in the open field was unchanged in GSH-deficient mice. In contrast, GSH-deficiency modulated the locomotor responses to mid-range doses of amphetamine (1.5 and 5 mg/kg, i.p.). Further, GSH-deficient mice displayed an increased locomotor response to low (2 and 3 mg/kg, i.p.) doses of phencyclidine (PCP). In conclusion, the data presented here show that even short-term GSH-deficiency has consequences for DA and 5-HT function. This was confirmed on both neurochemical and behavioral levels. How GSH and the monoamines interact needs further scrutiny. Moreover, the open field findings suggest reduced or altered N-methyl-d-aspartate (NMDA) receptor function in GSH-deficient mice. Thus, GSH-deficiency can lead to disturbances in DA, 5-HT and NMDA function, a finding that may have relevance for schizophrenia.

Functional dissociation between serotonergic pathways in dorsal and ventral hippocampus in psychotomimetic drug-induced locomotor hyperactivity and prepulse inhibition in rats.

Altered hippocampal function and brain serotonin activity are implicated in the development and symptoms of schizophrenia. We have previously shown that lesions of the median raphe nucleus, but not the dorsal raphe nucleus, produced a marked enhancement of locomotor hyperactivity induced by phencyclidine and disruption of prepulse inhibition. The dorsal and ventral hippocampus receive serotonin projections predominantly from the median raphe nucleus and dorsal raphe nucleus, respectively. Therefore, we investigated the effect of local lesions of serotonin projections into the dorsal and ventral hippocampus on psychotomimetic drug-induced locomotor hyperactivity and prepulse inhibition. Male Sprague-Dawley rats were anaesthetized with pentobarbitone and stereotaxically microinjected with 5 microg of the serotonergic neurotoxin 5,7-dihydroxytryptamine into either the dorsal or the ventral hippocampus. Two weeks after surgery, dorsal hippocampus-lesioned rats showed a 100% enhancement of the locomotor hyperactivity caused by phencyclidine treatment and a slight but significant reduction of the effect of amphetamine. Prepulse inhibition was significantly disrupted in lesioned rats and serotonin levels in the dorsal hippocampus were reduced by 80%. Rats with lesions of the ventral hippocampus showed 85% depletion of serotonin and partial disruption of prepulse inhibition, but no significant changes in the effect of phencyclidine or amphetamine. These results suggest that serotonin projections from the median raphe nucleus to the dorsal hippocampus play an important role in locomotor hyperactivity and prepulse inhibition in rats, animal models of aspects of schizophrenia. This suggests that these serotonin projections may be involved in the pathophysiology of schizophrenia symptomology.

Neural degeneration following chronic stimulant abuse reveals a weak link in brain, fasciculus retroflexus, implying the loss of forebrain control circuitry.

There is increasing evidence that the fasciculus retroflexus (FR) represents a 'weak link' following the continuous administration of drugs of abuse. A variety of drugs which predominantly potentiate dopamine, including D-amphetamine, methamphetamine, MDMA, cocaine, and cathinone, all induce degeneration in axons from lateral habenula, through the sheath of FR, to midbrain cells such as SN, VTA, and raphe. For some drugs, such as cocaine, this is virtually the only degeneration induced in brain. Continuous nicotine also selectively induces degeneration in FR, but in the other half of the tract, i.e. in axons from medial habenula through the core of the tract to interpeduncular nucleus. This phylogenetically primitive tract carries much of the negative feedback from forebrain back onto midbrain reward cells, and the finding that these descending control pathways are compromised following simulated drug binges has implications for theories of drug addiction but also psychosis in general.

Methamphetamine-induced neurotoxicity is attenuated in transgenic mice with a null mutation for interleukin-6.

Increasing evidence implicates apoptosis as a major mechanism of cell death in methamphetamine (METH) neurotoxicity. The involvement of a neuroimmune component in apoptotic cell death after injury or chemical damage suggests that cytokines may play a role in METH effects. In the present study, we examined if the absence of IL-6 in knockout (IL-6-/-) mice could provide protection against METH-induced neurotoxicity. Administration of METH resulted in a significant reduction of [(125)I]RTI-121-labeled dopamine transporters in the caudate-putamen (CPu) and cortex as well as depletion of dopamine in the CPu and frontal cortex of wild-type mice. However, these METH-induced effects were significantly attenuated in IL-6-/- animals. METH also caused a decrease in serotonin levels in the CPu and hippocampus of wild-type mice, but no reduction was observed in IL-6-/- animals. Moreover, METH induced decreases in [(125)I]RTI-55-labeled serotonin transporters in the hippocampal CA3 region and in the substantia nigra-reticulata but increases in serotonin transporters in the CPu and cingulate cortex in wild-type animals, all of which were attenuated in IL-6-/- mice. Additionally, METH caused increased gliosis in the CPu and cortices of wild-type mice as measured by [(3)H]PK-11195 binding; this gliotic response was almost completely inhibited in IL-6-/- animals. There was also significant protection against METH-induced DNA fragmentation, measured by the number of terminal deoxynucleotidyl transferase-mediated dUTP nick-end-labeled (TUNEL) cells in the cortices. The protective effects against METH toxicity observed in the IL-6-/- mice were not caused by differences in temperature elevation or in METH accumulation in wild-type and mutant animals. Therefore, these observations support the proposition that IL-6 may play an important role in the neurotoxicity of METH.