Melatonin attenuates the amphetamine-induced decrease in vesicular monoamine transporter-2 expression in postnatal rat striatum

The vesicular monoamine transporter-2 (VMAT-2) is responsible for packaging intraneuronal dopamine into synaptic vesicles in preparation for synaptic release and is a critical regulator of cytoplasmic dopamine levels and dopaminergic function. It has long been recognized that VMAT-2 is also a critical mediator of amphetamine-induced dopamine release. Amphetamine-induced lesions during development have the potential to produce numerous permanent abnormalities in neural circuitry and function. Therefore, in the present study, we investigated the effects of amphetamine on the levels of VMAT-2, α-synuclein and phosphorylated tyrosine hydroxylase in the striatum of neonatal rats. We found that chronic amphetamine administration in postnatal rats produces dopaminergic deficits in the striatum, including decreases in the levels of VMAT-2 and phosphorylated tyrosine hydroxylase. In addition, an increase in α-synuclein expression was observed in the striatum of postnatal rats following chronic amphetamine treatment. Furthermore, we identified a role of (10mg/kg) melatonin, a methoxyindole released from the pineal gland, in attenuating the detrimental effects of amphetamine on dopaminergic neurons.     

Histaminergic and dopaminergic traits in the human carotid body

Carotid body (CB) chemoreceptors are the main sensors detecting systemic hypoxia. Studies in animals revealed that dopamine and histamine may serve as transmitters between the chemoreceptor cells and the afferent nerve. To gain insight whether histamine and dopamine could play a role in the human CB and thus be important for the understanding of breathing disorders, we have investigated the chemosensory traits in human CBs from nine subjects of different ages obtained at autopsy. Immunohistochemistry revealed expression of histidine decarboxylase, vesicular monoamine transporter 2, histamine receptors 1 and 3 in virtually all chemosensory cells within the glomeruli of different ages. By contrast, catecholaminergic traits (tyrosine hydroxylase and vesicular monoamine transporter 1) were only detected in a subset of CB chemosensory cells at each age group while dopamine D2 receptors were expressed in the great majority of them. Our data suggest that histamine along with catecholamines may serve as transmitters between chemoreceptor cells and the afferent nerve in humans as well.     

尼古丁对PD大鼠黑质多巴胺能神经元变性的影响

目的 探讨尼古丁对帕金森病(PD)大鼠黑质多巴胺能神经元变性的影响及其机制. 方法 45只大鼠随机分为PBS对照组(CON)、生理盐水+ 脂多糖(NS)组、尼古丁+脂多糖(NIC)组,每组15只.黑质内立体定向注射脂多糖(LPS)或PBS后24h,免疫印迹法检测黑质诱导性一氧化氮合酶(iNOS)蛋白表达变化;黑质注射药物后14d,采用免疫组织化学法观察大鼠黑质酪氨酸羟化酶(TH)阳性神经元数量及OX-42阳性细胞形态学变化,RT-PCR及免疫印迹检测黑质TH mRNA及TH蛋白的表达水平. 结果 与CON组相比,NS组大鼠黑质iNOS表达明显增多,TH阳性神经元、TH mRNA及TH蛋白明显减少,小胶质细胞大多呈胞体大突起短粗的形态;NIC组黑质iNOS表达明显少于NS组,黑质TH阳性神经元、TH mRNA及TH蛋白表达较NS组明显增多,大部分小胶质细胞呈胞体小,突起细长的形态. 结论 尼古丁可以减轻LPS介导的多巴胺能神经元变性,对多巴胺能神经元有保护作用,其保护机制与抑制小胶质细胞激活、减少iNOS的表达有关.     

Opposing actions of chronic stress and chronic nicotine on striatal function in mice

Stress is a major risk factor in drug addiction development and relapse. Virtually all drugs of abuse act by increasing extracellular dopamine levels in the striatum. To gain an understanding of the interaction between stress and drug exposure, we studied the effects of concomitant chronic nicotine and chronic stress exposure on mouse striatal dopamine levels. C57Bl6/J mice were treated with nicotine in the drinking water or control solution for at least 6 weeks. Some mice were chronically stressed by daily exposure to cold, shaking or restrain. Nicotine-treated mice showed up-regulation of epibatidine binding in several brain regions. In mice treated with both chronic nicotine and stress, epibatidine binding was increased in all studied areas except the dorsal striatum. Therefore, microdialysis was used to measure extracellular dopamine levels in the dorsal striatum of mice chronically treated with nicotine, stress, or both. To have a measure of striatal response to different challenges, we performed microdialysis after acute injection of saline, nicotine, and cocaine. Chronic nicotine enhanced nicotine-dependent dopamine release, while chronic stress blunted the response to cocaine. When mice were subjected to both chronic nicotine and chronic stress, nicotine- and cocaine-dependent dopamine release was undistinguishable from that of control animals. In conclusion, our data suggest that chronic stress and chronic nicotine counteract each other's effect on dopamine release in the striatum. This effect might be mediated by changes in nicotinic acetylcholine receptor up-regulation. This "normalization" of striatal function when both nicotine and stress are present might help explain the comorbidity between stress-related disorders and drug abuse.     

Sex differences in negative affective response during nicotine withdrawal

This study examined physiological indicants of the neurobiological mediators of negative affect during acute nicotine withdrawal. Eighty subjects (41 male) were assigned to one of four groups (24-h deprived or nondeprived dependent smokers, occasional smokers, and nonsmokers) and participated in an instructed fear conditioning paradigm involving cued administration of electric shock. Negative affective response was measured with fear-potentiated startle during cues that signaled electric shock and during the postcue offset recovery period. Salivary cortisol and self-report measures were also collected. Fear-potentiated startle results indicated that affective recovery postcue offset was delayed in nicotine-deprived women. Nicotine-deprived women also displayed elevated cortisol levels throughout the fear conditioning procedure.     

Comparative immunohistochemical study of the dopaminergic systems in two inbred mouse strains (C57BL/6J and DBA/2J)

This study investigated possible neurochemical differences in the brain of two inbred mouse strains, C57BL/6J (C57) and DBA/2J (DBA) that in behavioral, memorization and learning tasks under normal and experimental conditions perform differently or often in an opposite manner. The immunohistochemical study, designed to investigate the dopaminergic system, identified many differences within the midbrain A10 area and less marked differences in areas A9 and A8. The number of dopamine transporter (DAT), vesicular monoamine transporter of type 2 (VMT) and tyrosine hydroxylase (TH) immunoreactive cell bodies was significantly higher in the midbrain of DBA mice than in C57 mice (on average +21.5%, P<0.001 in A10: +9.4% in A9, P<0.05: and +5.9% in A8, P<0.1). The distribution patterns of nerve fibres immunoreactive for same antisera also differed significantly in the two strains, especially at prelimbic, infralimbic and anterior cingulate cortical levels. In C57 mice these fibres were scanty whereas in DBA mice they were well represented. In the nucleus accumbens, also the territorial distribution of DAT immunoreactive nerve fibres differed in the two strains. In the midbrain, the galanin immunoreactive axons were more densely distributed in DBA than in C57 mice whereas neurotensin immunoreactive axons were more densely distributed in C57 than in DBA. These distinct immunohistochemical patterns could help to explain why performance differs in the two mouse strains.     

Acute nicotine enhances c-fos mRNA expression differentially in reward-related substrates of adolescent and adult rat brain

A number of studies have demonstrated that adolescent rodents are more sensitive to the rewarding effects of nicotine compared to adults. To help determine the potential brain circuitry involved, we investigated the effect of acute nicotine administration (0.4 or 0.8 mg/kg, s.c.) on the expression of c-fos mRNA in the brains of adolescent (P35) and adult (P67-70) male Wistar rats using in situ hybridization. Nicotine administration increased c-fos mRNA expression in several brain regions, including the central amygdala, locus coeruleus, nucleus accumbens core, paraventricular nucleus of the hypothalamus and lateral septum of adolescent and adult rats. Nicotine increased c-fos mRNA expression more robustly in the bed nucleus of the stria terminalis, nucleus accumbens shell and ventral tegmental area in adolescent rats. The current results suggest that nicotine may have greater activational effects in brain regions associated with reward in adolescent rats and may help to explain the differences between adolescents and adults in behavioral responses to nicotine.     

Non-serine-phosphorylated tyrosine hydroxylase expressing neurons are present in mouse striatum,accumbens and cortex that increase in number following dopaminergic denervation

Neurons partially expressing individual enzymes of dopamine (DA) biosynthesis, e.g. tyrosine hydroxylase (TH) or aromatic acid decarboxylase, are found in different areas of the central nervous system, continuously or transiently in normal and pathological conditions. This current study analyzed if TH neurons exist in target areas of ventral midbrain dopaminergic neurons and how they react to dopaminergic denervation.High power analysis of brain tissue sections revealed that TH-immunopositive neurons were present in striatum, accumbens and cortex - and several other brain areas - of healthy adult mice. DAergic denervation induced by stereotaxic injection of 6-hydroxydopamine into the medial forebrain bundle increased the number of TH expressing neurons in the striatum, accumbens and the cortex, up 40 d later. These TH neurons were not stained by specific antibodies recognizing TH phosphorylated at serine residues 19, 31 and 40, dopamine transporter and vesicular monoamine transporter type 2, but most of them expressed dopamine and cyclic AMP-regulated phosphoprotein 32 kDa.Thus, mouse striatum, accumbens and cortex contain neurons which express TH with low activity, and their number increases following dopamine depletion.     

Time-course of recovery of dopamine neuron activity during reinnervation of the denervated striatum by fetal mesencephalic grafts as assessed by in vivo voltammetry

Summary In vivo voltammetry was used to monitor dopamine (DA) neuron activity during the course of reinnervation of the initially denervated caudateputamen by grafted mesencephalic neurons. Fetal DA neurons were implanted as a cell suspension into the depth of the caudate-putamen in adult 6-hydroxydopamine-lesioned recipient rats. Recordings were performed over a period of 2.5–4 months, starting within a week after transplantation, using chronically implanted surface-treated multifiber carbon electrodes. The voltammetric method used in this study has generated considerable discussion centred on the ability of the multifiber electrodes to measure DA alone in vivo, but the results of previous studies have led to the conclusion that changes in the voltammetric signal most probably reflect dopaminergic terminal activity. It seems therefore possible to follow the time-course of changes in the voltammetric signal amplitude during the process of dopaminergic reinnervation of the host striatum from the grafts. A 6-hydroxydopamine lesion of the mesostriatal dopamine pathway caused a substantial (> 80%) reduction of the voltammetric signal within 8–10 days, and the low residual signal remained essentially unchanged for time periods up to at least 5 months in the non-grafted control rats. In 7 of 11 rats with DA-rich grafts there was a recovery of the signal amplitude to levels within, or close to, the range recorded from the striatum of normal intact rats. The increase was observed 6–8 weeks after grafting in the rats which had received the largest transplants, and at about 13–14 weeks after grafting in the rats which had received the smallest ones. The recovery of the signal amplitude, from baseline to maximal response, was quite rapid and typically developed between two or three recording sessions, i.e. over a period of one to two weeks. In contrast to the intact striatum, the recovered signal in the graft-reinnervated striata showed a progressive decline within one hour of sampling time at high sampling frequencies (1 per min to 1 per 3 min). Grafted striata also showed a larger response to systemically administered amphetamine than did intact striata. Since the changes in the voltammetric signal recorded with the multifiber electrode mainly reflect dopaminergic terminal activity, the results provide evidence that the intrastriatal DA-rich grafts are spontaneously active, and that the grafted DA neurons can restore DA neuro-transmission in the reinnervated part of the host caudate-putamen to levels which are within the normal range. From the time-course of changes in the voltammetric signal it can be estimated that the outgrowing DA fibers, after an initial maturation period, expand from the graft into the host striatum at a maximum rate of about 0.1 mm per week, and that the advancing front of graft-derived fibers may be capable of saturating the area around the electrode tip with new terminals within a time period of about 1–2 weeks. The characteristics of the signal seem compatible with the view that the activity of the individual grafted DA neurons is greater than that of the mesostriatal DA neurons in situ.     

Ultrastructural correlates of functional relationships between nigral dopaminergic or cortical afferent fibers and neuropeptide Y-containing neurons in the rat striatum

This study examines the ultrastructural relationships established by the nigrostriatal dopaminergic and the corticostriatal afferent fibers with neuropeptide Y (NPY)-containing neurons in the rat striatum. By means of dual immunolabeling procedures using peroxidase conjugated F(ab) fragments and ¹²⁵I-labeled protein A, direct appositions and morphologically defined synaptic contacts of the symmetrical type were visualized between tyrosine hydroxylase-labeled nerve terminals and NPY-labeled neurons. After deafferentation of the striatum from its cortical input direct appositions and asymmetrical synaptic contacts were evidenced between characteristic degenerative boutons and NPY-positive neurons in the striatum. These results suggest that striatal NPY interneurons undergo direct influence from both nigrostriatal dopaminergic and corticostriatal neuronal systems.     

Increased expression of preproneuropeptide Y and preprosomatostatin mRNA in striatum after selective serotoninergic lesions in rats

The levels of neuropeptide Y and somatostatin may change when serotoninergic neurotransmission is altered in different brain regions. To assess whether serotonin regulates the synthesis of these peptides, we measured the levels of preproneuropeptide Y (ppNPY) and preprosomatostatin (ppSOM) mRNA in different brain regions after intracerebroventricular injection of 5,7-dihydroxytryptamine (5,7-DHT), a selective serotonin neurotoxin. The mRNA of these peptides significantly increased in the striatum but not in hippocampus and frontal cortex. It thus appears that serotonin has an inhibitory effect on the biosynthesis of neuropeptide Y and somatostatin in striatum whereas it probably acts by stimulating the release of these peptides in hippocampus and frontal cortex.     

Effect of nitric oxide synthase inhibitor and NMDA receptor antagonist on the development of nicotine sensitization of nucleus accumbens dopamine release: An in vivo microdialysis study

We have previously found that the neuronal nitric oxide synthase inhibitor N-nitro-l-arginine (l-NNA) and the noncompetitive N-methyl-d-aspartate (NMDA) receptor antagonist MK-801 prevent behavioral sensitization to nicotine. This study aimed to investigate the effect of l-NNA and MK-801 on a neurochemical component of nicotine sensitization by evaluating the effect of the drugs on nicotine sensitization of nucleus accumbens dopamine (DA) release. Sprague–Dawley rats were pretreated with l-NNA (15 mg/kg, i.p.), MK-801 (0.3 mg/kg, i.p.), or saline 30 min before injection of nicotine (0.4 mg/kg, s.c., once daily) for seven consecutive days. Twenty-four hours after the last drug injection, animals were challenged with local perfusion of 5 mM nicotine into the shell of nucleus accumbens for 60 min and DA release was monitored using in vivo microdialysis. In rats treated with repeated nicotine, acute nicotine challenge induced a greater increase of accumbal DA release than in saline-treated animals (maximal DA response = 969 ± 235% (mean ± S.E.M.) of basal level versus 520 ± 93%, p = 0.042). Co-administration of l-NNA or MK-801 with nicotine attenuated an increase of DA release elicited by acute nicotine challenge, compared with nicotine alone (maximal DA response = 293 ± 58% and 445 ± 90% of basal level, respectively versus 969 ± 235%, p = 0.004 and p = 0.013, respectively). These data demonstrate that l-NNA and MK-801 block the development of nicotine sensitization of nucleus accumbens DA release, further supporting the involvement of nitric oxide and NMDA receptors in the development of behavioral sensitization to nicotine.     

DOI诱导的Wistar大鼠头部抽动模型脑内VMAT2的表达

目的 用DOI诱导大鼠头部抽动建立Tourette综合征动物模型,研究该动物模型脑内VMAT2的表达.方法 30只Wistar大鼠随机分为对照组、连续腹腔注射DOI14d和21d组,应用RT-PCR法检测黑质VMAT2mRNA表达,应用免疫组织化学法观察大鼠纹状体vMAT2蛋白的表达.结果 大鼠注射DOI14d和21d...     

Changed accumbal responsiveness to alcohol in rats pre-treated with nicotine or the cannabinoid receptor agonist WIN 55,212-2

Alcohol, nicotine, and cannabinoid acutely increase the activity of the mesolimbic dopamine (DA) pathway. Although polysubstance consumption is a common pattern of abuse in humans, little is known about dopamine release following pre-exposure to these drugs. The purpose of this study was to test whether alcohol-induced dopamine release into the nucleus accumbens (NAc) shell is modified by different pre-treatments: water (i.g.), alcohol (1 g/kg, i.g.), nicotine (0.4 mg/kg, s.c.), and WIN 55,212-2 (1 mg/kg, s.c.). Male Wistar rats were treated (i.g.) for 14 days with either water or alcohol. In the following 5 days rats were injected (s.c.) with vehicle, nicotine, or WIN 55,212-2. Finally, a cannula was surgically implanted into the NAc shell and alcohol-induced extracellular dopamine release was monitored in freely moving rats. Alcohol (1 g/kg; i.g.) only increased the release of dopamine when animals were previously treated with water. This DA increase was markedly inhibited by (subchronic) treatment (5 days) with nicotine or WIN 55-212-2 as well as by previous (chronic) exposure to alcohol (14 days). These data demonstrate that pre-treatment with nicotine and the cannabinoid agonist WIN 55,212-2 is able to change the sensitivity of the NAc shell in response to a moderate dose of alcohol. Therefore, cannabinoid and nicotine exposure may have important implications on the rewarding effects of alcohol, because these drugs lead to long-lasting changes in accumbal dopamine transmission.     

正畸牙移动过程中尼古丁摄入对牙周组织影响

背景：吸烟是严重影响牙周组织和牙根健康的危险因素之一,烟草中的尼古丁会加速牙周病患者牙周组织的破坏。 目的：分析正畸牙移动过程中不同剂量尼古丁作用下牙周组织内环氧化酶2及mRNA表达的变化规律。 方法：将110只SD大鼠随机分为5组,空白对照组10只,生理盐水组和尼古丁0.5,0.75,1 mg/kg组各25只。除空白组外所有大鼠使用50 g力牵拉一侧上颌第1磨牙向近中移动。生理盐水组每日腹腔注射0.1 mL生理盐水;尼古丁组每日腹腔注射0.5,0.75,1 mg/kg尼古丁酒石酸溶液。各组大鼠分别在加力1,3,5,7,14 d时处死取上颌组织,苏木精-伊红染色观察牙周组织变化,免疫组织化学染色计数破牙骨质细胞阳性细胞,原位杂交染色法检测环氧化酶2在牙周组织中表达的平均吸光度值。 结果与结论：尼古丁各剂量组在各加力时间点破牙骨质细胞数目均高于未注射尼古丁组,且环氧化酶2阳性细胞表达强度也均高于未注射尼古丁组。随尼古丁注射剂量增大,破牙骨质细胞数目也逐渐增加(P < 0.05),加力7 d时各组破牙骨质细胞数目均达到峰值;环氧化酶2阳性细胞表达强度也随尼古丁注射剂量增大而增强(P < 0.05),加力5 d时表达强度达到峰值。结果表明,在相同加力时间点,破牙骨质细胞数目随剂量增大而增多,且环氧化酶2阳性细胞表达强度也随剂量增加而增强。正畸牙移动过程中的尼古丁摄入会造成牙周组织的破环,且尼古丁摄入剂量的高低直接影响牙周组织的破坏程度。 中国组织工程研究杂志出版内容重点：组织构建;骨细胞;软骨细胞;细胞培养;成纤维细胞;血管内皮细胞;骨质疏松;组织工程     

L-Dopa treatment abolishes the numerical increase in striatal dopaminergic neurons in parkinsonian monkeys

The striatum harbors a population of dopaminergic interneurons that increases in number in animal models of Parkinson's disease (PD), presumably to compensate for dopamine (DA) depletion. The purpose of the present study was to determine the fate of striatal dopaminergic neurons in parkinsonian monkeys in which striatal DA depletion had been alleviated by systemic administration of l-dopa. The number of striatal dopaminergic neurons, visualized with tyrosine hydroxylase (TH) immunohistochemistry, was measured in three groups of cynomolgus (Macaca fascicularis) monkeys: (1) normal untreated monkeys; (2) monkeys rendered parkinsonian following systemic injection of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), but otherwise untreated; and (3) MPTP-intoxicated monkeys that received oral l-dopa on a chronic basis. In agreement with previous studies, the number of striatal TH-positive (TH+) neurons in l-dopa-free parkinsonian monkeys was significantly higher (p<0.05) than in normal (non-parkinsonian) monkeys. However, this increase was abolished in parkinsonian monkeys that received l-dopa treatment. In fact, the number of striatal TH+ neurons in l-dopa-treated parkinsonian monkeys was not significantly different (p>0.05) from values obtained in normal monkeys. These findings suggest that the DA concentration regulates the numerical density of this ectopic neuronal population, a phenomenon that is more likely the result of a shift in the phenotype of preexistent striatal interneurons rather than the recruitment of newborn neurons that would eventually develop a DA phenotype. Our data also reinforce the hypothesis that striatal TH+ neurons act as local DA source and, as such, are part of a compensatory mechanism that could be artificially enhanced to alleviate or delay PD symptoms.     

Analysis of vesicular monoamine transporter 2 polymorphisms in Parkinson’s disease

Generation of reactive oxygen species during dopamine (DA) oxidation could be one of the factors leading to the selective loss of nigral dopaminergic neurons in Parkinson’s disease (PD). Vesicular monoamine transporter type 2 (VMAT2) proteins in nerve terminals uptake dopamine into synaptic vesicles, preventing its cytoplasmic accumulation and toxic damage to nigral neurons. Polymorphisms in VMAT2 gene and in its regulatory regions might therefore serve as genetic risk factors for PD. In the present study, we have analyzed 8 single-nucleotide polymorphisms (SNPs) located within/around the VMAT2 gene for association with PD in an Italian cohort composed of 704 PD patients and 678 healthy controls. Among the 8 SNPs studied, only the 2 located within the promoter region (rs363371 and rs363324) were significantly associated with PD. In the dominant model, odds ratios were 0.72 (95% confidence interval [CI]: 0.6–0.9, p < 0.005) for rs363371 and 0.76 (95% CI: 0.6–0.9, p = 0.01) for rs363324; in the additive model, odds ratios were 0.78 (95% CI: 0.65–0.94, p = 0.008) for rs363371 and 0.85 (95% CI: 0.7–20.92, p = 0.04) for rs363324. There were no significant relationships between the remaining SNPs (rs363333, rs363399, rs363387, rs363343, rs4752045, and rs363236) and the risk of sporadic PD in any genetic model. This study adds to the previous evidence suggesting that variability in VMAT2 promoter region may confer a reduced risk of developing PD, presumably via mechanisms of gene overexpression.     

Effect of prenatal exposure to diesel exhaust on dopaminergic system in mice

Diesel exhaust (DE) is composed of particles and gaseous compounds. It has been reported that DE causes pulmonary and cardiovascular disease. We have previously reported that fetal exposure to DE had deleterious effects to the reproductive system of mice offspring. However, there is still little known about the effects of prenatal exposure to DE to the central nervous system (CNS). In the present study, we found that prenatal exposure to DE induced reduction of locomotion, furthermore, dopamine (DA) turnover was significantly decreased in the striatum and nucleus accumbens. These results suggest that prenatal exposure to DE has an effect on the CNS. Hypolocomotion could be due to a decrease in DA turnover associated with DA nervous system abnormality. The present study provides the possibility that maternally inhaled DE might influence the development of central dopaminergic system and result in behavior disorder.