Phenytoin potentiates methamphetamine-induced behavior in mice

We demonstrated that stereotyped behavior and tremor induced by methamphetamine (MA) were potentiated by pretreatment with phenytoin (PNT) in mice. Similar enhancing effects were obtained by pretreatment with carbamazepine. Gas chromatographic study demonstrated that pretreatment with PNT increased MA concentrations in the brain to approximately 2.5 times of control level. The increased MA concentrations were thought to be a major factor for the observed potentiation of MA-induced behavior by PNT. However, all MA-induced behavior were not equally potentiated; tremor was enhanced more than stereotypy. These results suggest that central neuronal mechanisms may also be involved in PNT-potentiated MA-induced behavior in mice.     

甲基苯丙胺诱导小鼠行为敏化模型的构建与评估

目的:探讨不同剂量水平甲基苯丙胺(MA)所诱导的小鼠行为敏化模型的构建与评估方法。方法:40只C57BL/6J小鼠,随机分为5组:生理盐水对照组(NS)和0.5、2、5、10mg·kg-1MA剂量组,各组在形成期连续5d每天腹腔注射(ip)不同剂量药物并记录自主活动情况,转化期停药观察2d后,在d8表达期给予最后一次等量剂量MA,并记录自主活动情况。结果:(1)不同剂量MA作用于实验小鼠,在小剂量水平即能够诱导出明显的行为敏化现象,且随着药物浓度增大,呈现剂量依赖性变化;(2)在10mg·kg-1大剂量水平,小鼠表现为明显的刻板行为,在表达期同样出现了刻板行为的增强现象。结论:本实验为不同剂量的小鼠MA敏化模型提供了比较标准的构建和评估方法;2mg·kg-1MA作用于实验小鼠,诱导出了明显的行为敏化现象,同时其他精神运动改变如刻板行为出现较少,是构建药物依赖行为敏化模型较理想的剂量;利用该行为敏化模型可进一步分析和评估药物依赖治疗性药物的疗效。     

噻诺啡灌胃给药对小鼠甲基苯丙胺行为敏化的影响

目的:探讨新型丁丙诺啡同系物-噻诺啡,灌胃(ig)给药对小鼠甲基苯丙胺行为敏化过程的影响。方法:测定小鼠的自主活动,观察ig噻诺啡对小鼠的自主活动及单次给予甲基苯丙胺所诱导的小鼠高活动性的影响。建立甲基苯丙胺诱导的小鼠行为敏化模型,观察噻诺啡对行为敏化形成、转化及表达的影响。结果:(1)单次ig噻诺啡(1 2 5 - 5 0mg·kg-1)可剂量依赖性地抑制小鼠的自主活动(P <0 . 0 1) ,其作用多次给药后产生耐受;(2 )噻诺啡对单次给予甲基苯丙胺所诱导的小鼠的高活动性无明显影响;(3)噻诺啡对甲基苯丙胺诱导小鼠行为敏化的形成和表达无明显作用,却可显著抑制敏化的转化过程(P <0 . 0 5 )。结论:ig噻诺啡可抑制小鼠中枢神经系统,阻断甲基苯丙胺诱导小鼠产生行为敏化的转化过程,提示噻诺啡对甲基苯丙胺的成瘾行为具有一定的干预作用。     

Cerebral dopamine function in rats following withdrawal from one year of continuous neuroleptic administration

Continuous administration of trifluoperazine (2.5--3.5 mg/kg/day) or thioridazine (30--40 mg/kg/day) to rats for 12 months enhanced the stereotyped response to apomorphine (0.5 mg/kg s.c.), increased dopamine 1--150 muM) stimulation of striatal adenylate cyclase, increased KD and Bmax for dopamine (10(-4) M) specific 3H-spiperone striatal binding and produced spontaneous mouthing movements. On drug withdrawal, spontaneous locomotor activity was enhanced after 2 weeks and the enhanced stereotyped response was maintained for up to 1 month. Spontaneous mouthing had disappeared 2 weeks after drug withdrawal. The increase in Bmax for 3H-spiperone binding was maintained for up to 3 months after drug removal, but KD reverted to control levels by 2 weeks. In contrast, the dopamine stimulation of striatal adenylate cyclase remained enhanced for the 6 month withdrawal period. Administration of trifluoperazine (0.7--0.9 mg/kg/day) or thioridazine (6--8 mg/kg/day) for 12 months produced a less marked effect than administration of the higher dose. No enhancement of effect was observed on drug withdrawal and the initial changes disappeared rapidly on removal of drug. Supersensitivity of striatal dopamine mechanisms produced by continuous long-term neuroleptic administration differs from that produced by shorter treatment periods since no enhancement of effect occurs on drug withdrawal. The behavioural and biochemical components of the supersensitivity show variable time courses and in particular the enhanced stimulation of striatal adenylate cyclase persists for at least 6 months. Such effects may be of relevance to tardive dyskinesias in man.     

Do preclinical findings of methamphetamine-induced motor abnormalities translate to an observable clinical phenotype?

This review summarizes the preclinical literature of the effects of methamphetamine (MA) on subcortical dopaminergic and GABAergic mechanisms underlying motor behavior with the goal of elucidating the clinical presentation of human MA-induced movement disorders. Acute and chronic MA exposure in laboratory animal can lead to a variety of motor dysfunctions including increased locomotor activity, stereotypies, diminished or enhanced response times, and parkinsonian-like features. With the exception of psychomotor impairment and hyperkinesia, MA-induced movement disorders are not well documented in humans. This review attempts to draw parallels between the animal and human changes in basal ganglia neurochemistry associated with MA exposure and offers explanations for why a parkinsonian phenotype is not apparent among individuals who use and abuse MA. Significant differences in the expression of neurotoxicity and presence of multiple environmental and pharmacologic confounds may account for the lack of a parkinsonian phenotype in humans despite evidence of altered dopamine function.     

Gastrodia elata bl attenuates methamphetamine-induced dopaminergic toxicity via inhibiting oxidative burdens

It has been recognized that Gastrodia elata Bl (GE), an oriental herb medicine, ameliorates various neurological disorders, that GE modulates the monoaminergic and GABAergic systems, and that GE possess antioxidant activities. We examined whether GE affects methamphetamine (MA)-induced striatal dopaminergic toxicity in mice. Treatment with MA (7.5 mg/kg, i.p. × 4) resulted in significant decreases in behavioural activity (as shown by locomotor activity and rota rod performance), dopamine level, tyrosine hydroxylase (TH) activity, and TH protein expression (as evaluated by immunocytochemistry and western blot analysis). In addition, MA treatment showed significant increases in lipid peroxidation [as evaluated by 4-hydroxy-2-nonenal (4-HNE) expression and malondialdehyde formation], protein oxidation (as shown by protein carbonyl expression and its formation), and reactive oxygen species (ROS) formation. Treatment with GE significantly attenuates MA-induced behavioural and dopaminergic impairments, and oxidative stresses in a dose-dependent manner. Our results suggest that GE treatment shows anti-dopaminergic effects in response to MA insult via, at least in part, inhibiting oxidative stresses in the striatum of the mice.     

Scopolamine prevents augmentation of stereotypy induced by chronic methamphetamine treatment

Cholinergic neurotransmission has been implicated in various forms of neural plasticity such as kindling and learning. We have previously shown that blockade of muscarinic cholinergic receptors prevents the development of locomotor sensitization to methamphetamine. The present study was conducted to examine whether scopolamine, a muscarinic cholinergic antagonist, would also block augmentation of stereotypy induced by chronic methamphetamine (MA) treatment. Rats treated with MA (2.5 mg/kg, SC) for 10 days indicated significantly enhanced stereotyped behavior when tested with MA (2.5 mg/kg) after a 7-to 8- day withdrawal. Pretreatment with scopolamine (3 mg/kg) prior to MA administration prevented the augmentation of stereotypy. Rats treated with scopolamine alone showed no difference in MA-induced stereotypy compared to those treated with saline. Scopolamine methylbromide, a derivative of scopolamine that does not easily cross the blood-brain barrier, had no effect on the augmentation of stereotypy. These results suggest that stimulation of central muscarinic cholinergic receptors plays a role in the development of sensitization to the stereotypy stimulating effect of methamphetamine.     

归元片对小鼠甲基苯丙胺行为敏化的影响

目的:探讨中药复方制剂归元片对甲基苯丙胺行为敏化的影响.方法:测定小鼠的自主活动,观察归元片对小鼠自主活动及甲基苯丙胺急性活动增强效应的影响.小鼠慢性甲基苯丙胺处理,建立甲基苯丙胺诱导的行为敏化小鼠模型,观察归元片对甲基苯丙胺行为敏化获得和表达的影响.结果:归元片呈剂量依赖性降低小鼠的活动性,对甲基苯丙胺的急性高活动效应有抑制作用.归元片阻断小鼠甲基苯丙胺行为敏化的获得和表达.结论:归元片对中枢神经系统功能具有抑制作用,能抑制甲基苯丙胺行为敏化的获得和表达,提示归元片能抑制甲基苯丙胺的奖赏效应,可能对防治甲基苯丙胺的滥用和成瘾有效.     

Amphetamine isomers: influences on locomotor and stereotyped behavior of cats

Catecholamine release and reuptake are considerably more stereoselective at norepinephrine than at dopamine nerve terminals, suggesting that pronounced differences in the influence of amphetamine isomers on particular behaviors favors norepinephrine mediation while similar actions of these isomers indicates a predominant role for dopamine. (+)-Amphetamine is markedly more potent than its (?)-isomer in stimulating locomotor activity of the cat while the two isomers differ less in provoking stereotyped behavior. These findings support a major role for brain norepinephrine in mediating amphetamine-induced locomotor enhancement, while dopamine may be more important in facilitating stereotyped behavior. Besides inducing stereotyped behavior, L-Dopa greatly enhances locomotor activity, which suggests an important role for dopamine in mediating locomotor activation.     

Alterations in diurnal and nocturnal locomotor activity in rats treated with a monoamine-depleting regimen of methamphetamine or 3,4-methylenedioxymethamphetamine

RATIONALE: The long-term neurochemical effects produced by the repeated administration of methamphetamine (MA) and 3,4-methylenedioxymethamphetamine (MDMA) are well documented; however, the functional consequences have not been clearly defined. OBJECTIVE: The present study was designed to investigate whether rats treated with a monoamine-depleting regimen of MA or MDMA exhibit disturbances in locomotor activity during the diurnal and nocturnal cycles. METHODS: Rats were treated with the vehicle or a monoamine-depleting regimen of MA or MDMA (10 mg/kg, IP, every 2 h for four injections on a single day). One week after drug treatment, the rats were placed in residential activity chambers and their locomotor activity was monitored for the next 7-day/night cycles. RESULTS: MA-treated rats exhibited depletions of striatal dopamine and serotonin content of approximately 70%, whereas MDMA-treated rats showed depletions of striatal serotonin content of approximately 50%. Rats treated with MA demonstrated a significant reduction in diurnal, but not nocturnal, locomotor activity, whereas MDMA-treated rats exhibited significant reductions in both diurnal and nocturnal locomotor activity. Analysis of the difference in activity between the nocturnal and diurnal cycles revealed that MA-treated animals exhibited a significantly greater change in activity as compared to that observed in vehicle- and MDMA-treated rats. CONCLUSIONS: Although it is unknown whether the adaptations in locomotor activity observed in MA- and MDMA-treated rats are due to the loss of dopamine and/or serotonin, these data suggest that the administration of a monoamine-depleting regimen of MA or MDMA results in alterations in light-cycle-dependent locomotor activity.     

Gender differences in modulatory effects of tamoxifen upon the nigrostriatal dopaminergic system

It has been demonstrated that the gonadal steroid hormone estrogen can exert neuroprotective effects upon the nigrostriatal dopaminergic (NSDA) system against methamphetamine (MA)-induced neurotoxicity in female, but not male, mice. In contrast, the anti-estrogen, tamoxifen (TMX) can function as a NSDA neuroprotectant within both female and male mice. In an attempt to understand these effects of TMX, the effects of this anti-estrogen upon both behavioral and neurochemical indices of NSDA function were examined within female and male mice following treatment with MA. In general, TMX exerted markedly different (bi-directional) effects upon NSDA function between female and male mice. Notably, treatment with TMX resulted in a relative decrease in striatal dopamine (DA) and 3,4-dihydroxyphenylacetic acid (DOPAC) concentrations within male mice and a relative increase in female mice when treated with MA to produce a significant gender difference. Similar effects were obtained for locomotor behaviors related with NSDA function. That is, TMX produced increases in horizontal activity, number of movements and total distance traveled within MA-treated female mice resulting in statistically significant gender differences for the two former parameters. For non-locomotor behaviors, like time occupying the center and margin of the cage, TMX-treated male mice showed statistically significant increases and decreases compared within TMX-treated female mice, respectively. These results show that in contrast to the similar neuroprotective effects of TMX upon MA-induced NSDA neurotoxicity, a number of other NSDA indices induced by MA show markedly different response profiles between TMX-treated female and male mice.     

No tolerance to antiaggressive effect of d-amphetamine in mice

Agonistic, locomotor, and stereotyped behavior were measured in male Swiss-Webster mice in their home cage, normally shared with a female, while confronting an intruder mouse. Acute administration of d-amphetamine (2, 4, 8 mg/kg, IP) to resident mice decreased the frequency of attacks toward an untreated intruder, increased the resident's locomotor activity, and induced a small amount of stereotyped behavior. Redetermination of dose-effect functions during chronic treatment (8 or 16 mg/kg/day) indicated that tolerance did not develop to the antiaggressive effect of d-amphetamine. By contrast, the chronically treated mice showed sensitization to amphetamine-induced stereotypies and a diminished sensitivity to the drug's enhancement of locomotor activity. Subsequent tests with cocaine indicated no differences between amphetamine-maintained and saline control animals, providing no evidence for cross-tolerance or cross-sensitization between cocaine's and amphetamine's effects on attack, locomotion, and stereotypies.     

Effect of quinpirole on striatal dopamine release and locomotor activity in nicotine-treated mice

The effect of chronic oral nicotine treatment which in its intermittent delivery resembles human smoking was studied on the sensitivity of dopamine autoreceptors in mice. On the 50th day of nicotine administration in the drinking water or after 23-25 h withdrawal quinpirole (D2/D3 agonist, 0.01-0.1 mg/kg s.c.) was given, and accumbal and dorsal striatal dopamine outflow, locomotor activity and body temperature were measured. Dorsal striatal extracellular dopamine concentration and locomotor activity were found to be elevated during nicotine administration. Chronic nicotine did not alter the effects of small, autoreceptor preferring doses of quinpirole on accumbal or dorsal striatal dopamine, locomotor activity or body temperature. However, quinpirole's locomotor activity reducing effect was slightly diminished in mice treated repeatedly with nicotine (0.4 mg/kg twice daily for 10 days s.c.). Thus, although repeated nicotine treatment for 5-14 days decreases dopamine autoreceptor sensitivity, after long-term oral nicotine treatment such a decrease is not seen. Thus, the changes occurring in the sensitivity of D2-like dopamine receptors probably play a minor role in regulating the dopaminergic transmission during long-term nicotine administration.     

Continuous phencyclidine treatment induces schizophrenia-like hyperreactivity of striatal dopamine release.

Functional dopaminergic hyperactivity is a key feature of schizophrenia. Recent in vivo imaging studies have demonstrated greater striatal dopamine release in response to amphetamine challenge in schizophrenia subjects than in normal controls. N-methyl-D-aspartate (NMDA) receptors are known to play a prominent role in regulation of striatal dopamine release. In humans, NMDA antagonists induce a psychotic state that closely resembles schizophrenia. The present study investigates the degree to which chronic continuous administration of the NMDA antagonist phencyclidine (PCP) induces schizophrenia-like hyperreactivity of striatal dopamine release to amphetamine in rodents. Rats were treated with 10 or 15 mg/kg/d PCP for two weeks by osmotic minipump, and striatal dopamine release to amphetamine challenge (1 mg/kg) was monitored by microdialysis. PCP-treated rats showed significant enhancement in amphetamine-induced dopamine release, along with significantly enhanced locomotor activity. These findings support the concept that NMDA receptor dysfunction may contribute to dopaminergic dysfunction in schizophrenia.     

Intake of fermented soybean (natto) increased locomotor activity in mice

We fed mice food granules containing fermented soybean (natto in Japanese) powder (hereafter "natto granules") for 14 d to investigate whether natto granules had any effects on mouse behavior. We noted an enhancement of locomotor activity in natto-granule-fed mice compared to control and soybean-pellet-fed mice. This enhanced locomotor activity was blocked by a low dose of haloperidol (1 microg/kg i.p.), a dopamine receptor antagonist, but not by methysergide, a serotonin 5-HT(1/2) receptor antagonist. The results suggest that the enhanced locomotor activity induced by continuous intake of natto granules in mice is sensitive to haloperidol.     

A role for casein kinase 1 epsilon in the locomotor stimulant response to methamphetamine

Rationale  We previously colocalized a quantitative trait locus (QTL) for sensitivity to the locomotor stimulant effects of methamphetamine (MA) with a QTL for expression of casein kinase 1 epsilon (Csnk1-ɛ) in the nucleus accumbens (NAc). Subsequently, we identified a single nucleotide polymorphism in CSNK1E (rs135745) that was associated with increased sensitivity to the subjective effects of d-amphetamine in healthy human subjects. Based on these results, we hypothesized that differential expression of Csnk1-ɛ causes differential sensitivity to MA-induced locomotor activity in mice. Objective  In the present study, we used PF-670462 (PF), which is a selective inhibitor of Csnk1-ɛ, to directly evaluate the role of Csnk1-ɛ in the locomotor stimulant response to MA in male C57BL/6J mice. Methods  We administered vehicle, PF, MA, or MA + PF, either via intraperitoneal injections or bilateral intra-NAc microinjections. We also examined Darpp-32 phosphorylation in mice receiving intraperitoneal injections. Results  Intraperitoneal PF (20–40 mg/kg) attenuated the locomotor stimulant response to MA (2 mg/kg) without affecting baseline activity. The high dose of PF also significantly inhibited MA-induced phosphorylation of Darpp-32, providing a potential mechanism by which Csnk1-ɛ contributes to MA-induced locomotor activity. Furthermore, microinjection of PF (5 μg/side) into the NAc completely blocked the locomotor stimulant response to MA (2.5 μg/side) without affecting baseline activity. Conclusions  These results provide direct evidence that Csnk1-ɛ is crucial for the locomotor stimulant response to a moderate dose of MA and suggest that genetic polymorphisms affecting Csnk1-ɛ expression or function could influence sensitivity to amphetamines in both mice and humans. Funding: DA021336-02 (A.A.P.), DA09397 (P.V.), 2T32DA007255 (C.D.B.), 5T32GM07281 (M.G.D.).     

甲基苯丙胺致大鼠神经毒性及纹状体硝化作用的改变

目的探讨甲基苯丙胺(methamphetamine,MA)所导致的大鼠神经毒性及纹状体硝化作用的改变。方法建立MA给药模型,对照组给予等量生理盐水;观察两组大鼠的行为学改变,体温变化,纹状体中NO含量,NOS活性和蛋白质硝化水平的变化情况。结果MA组大鼠刻板行为评分和体温均高于对照组(P<0.01);与对照组相比,MA组大鼠纹状体NO含量及NOS活性增加(P<0.01);纹状体蛋白硝化水平明显增加(P<0.01),差异有显著性。结论MA可导致大鼠行为学改变和体温变化,大鼠脑组织NO含量、NOS活性及蛋白硝化水平的增高可能是MA中枢神经系统损伤的重要机制。     

Methamphetamine-induced behavioral effects and releases of brain catecholamines and brain concentrations of methamphetamine in mice

The characteristic behavioral effect of methamphetamine (MA) at 2.5 mg/kg was enhanced locomotor activity which lasted over 2.5 hr. At 10.0 mg/kg MA, stereotyped behavior was predominant and lasted over 3 hr. The behavioral effect of 5.0 mg/kg MA was of the mixed type. MA at 5.0 and 10.0 mg/kg lowered the brain NE level from 2 hr after drug treatment, while the accumulation of MHPG-SO4 was increased over 2 hr at 2.5 and 5.0 mg/kg MA. The accumulation of HVA was significantly increased at 10.0 mg/kg MA over 3 hr. Accordingly, the behavioral effects of MA at the earlier period were compatible with the biochemical effects of MA. The behavioral effects during the 2- to 4-hr period, however, seem to be unrelated to the actions on brain catecholamines. Measurement of brain MA concentrations revealed that approx. 2 micrograms/g in the brain may be necessary to produce enhanced locomotor activity and the increased accumulation of brain MHPG-SO4. It appeared that approx. 8 to 9 micrograms/g MA in the brain was required to produce characteristic stereotyped behavior and the increased accumulation of HVA. Therefore, the behavioral and biochemical effects of MA were correlated with the brain MA concentrations.     

Effects of dopaminergic drugs on phencyclidine-induced behavior in the rat

Phencyclidine-induced behavior was studied in combination with drugs which block or enhance central dopamine activity. Haloperidol inhibited phencyclidine-induced stereotyped behavior and locomotor activity, and increased ataxia at all dose levels used (2.0, 4.0 and 6.0 mg/kg). Apomorphine potentiated phencyclidine-induced stereotypy at all doses in later post-injection periods (beyond 30 min). The effects of apomorphine on phencyclidine-induced locomotor activity were dose-dependent, showing inhibition at 2.0 mg/kg and enhancement at 4.0 and 6.0 mg/kg. These findings support suggested involvement of dopamine in phencyclidine-induced behavior and indicate the value of concurrent assessment of different phencyclidine-induced behavior for evaluating neurotransmitter effects.     

Protective effects of pseudoginsenoside-F11 on methamphetamine-induced neurotoxicity in mice

In the present study, pseudoginsenoside-F(11) (PF(11)), a saponin that existed in American ginseng, was studied on its protective effect on methamphetamine (MA)-induced behavioral and neurochemical toxicities in mice. MA was intraperitoneally administered at the dose of 10 mg/kg four times at 2-h intervals, and PF(11) was orally administered at the doses of 4 and 8 mg/kg two times at 4-h intervals, 60 min prior to MA administration. The results showed that PF(11) did not significantly influence, but greatly ameliorated, the anxiety-like behavior induced by MA in the light-dark box task. In the forced swimming task, PF(11) significantly shortened the prolonged immobility time induced by MA. In the appetitively motivated T-maze task, PF(11) greatly shortened MA-induced prolonged latency and decreased the error counts. Similar results were also observed in the Morris water maze task. PF(11) significantly shortened the escape latency prolonged by MA. There were significant decreases in the contents of dopamine (DA), 3,4-dihydroxyphenacetic acid (DOPAC), homovanillic acid (HVA), and 5-hydroxyindoacetic acid (5-HIAA) in the brain of MA-treated mice. PF(11) could partially, but significantly, antagonize MA-induced decreases of DA. The above results demonstrate that PF(11) is effective in protection of MA-induced neurotoxicity and also suggest that natural products, such as ginseng, might be potential candidates for the prevention and treatment of the neurological disorders induced by MA abuse.