雌激素对6-羟基多巴胺损伤黑质多巴胺能神经元的保护作用

本研究以P50听觉诱发电位(P50 auditory evoked potential, P50)和酪氨酸羟化酶(tyrosine hydroxylase, TH)阳性细胞计数作为黑质功能和形态学指标,动态追踪研究雌激素对6-羟基多巴胺(6-hydroxydopamine, 6-OHDA)损伤黑质多巴胺(dopamine, DA)能神经元的作用.将大鼠分为4组:(1)正常雌性大鼠对照组;(2)单纯帕金森氏病(Parkinson's disease, PD)模型组;(3)双侧去卵巢PD模型组;(4)去卵巢回补3d雌激素的PD模型组.在大鼠清醒和安静的生理状态下连续14d记录黑质的P50,并检测黑质TH 细胞数目的变化.结果显示:单纯PD模型大鼠黑质P50的T/C值较正常雌鼠降低40.60%(P<0.01),其损伤侧黑质TH 细胞数目减少64.74%(P<0.01);去卵巢PD模型大鼠黑质P50的T/C值较单纯PD模型大鼠进一步降低45.88%(P<0.01),同时其黑质TH 细胞数目值也进一步减少57.26%(P<0.01),表明急性缺乏生理水平性腺雌激素将增大6-OHDA损伤黑质DA能神经元的程度,同时使黑质的感觉门控(sensory gating, SG)功能明显受损;去卵巢后回补3d生理剂量雌激素,可明显改善大鼠黑质的SG功能,提高TH 细胞数量(与去卵巢PD模型大鼠比较,P<0.01),其黑质损伤程度与单纯PD模型大鼠相当.以上结果提示,生理水平的雌激素具有提高黑质DA能神经元对伤害性刺激耐受性的神经保护作用.缺乏性腺源性的雌激素时,及时给予生理剂量的雌激素可以减轻神经毒素6-OHDA对黑质DA能神经元结构和功能的损伤.     

Putative cholinergic elements in the photosensory pineal organ and retina of a teleost,Phoxinus phoxinus L. (Cyprinidae)

Summary Putative cholinergic neurons in the photosensory pineal organ of a cyprinid teleost, the European minnow, were studied by use of choline acetyltransferase (ChAT) immunocytochemistry and acetylcholinesterase (AChE) histochemistry. Pinealofugally projecting neurons were visualized using retrograde HRP-filling through their cut axons. For comparison, the distribution of choline acetyltransferase immunoreactivity (ChAT-IR) and AChE-positive elements in the retina was investigated.While the distributional patterns of ChAT-IR and strongly AChE-positive perikarya in the retina are similar and may represent the same neuronal population, ChAT-IR and AChE-positive elements in the pineal organ appear to belong to separate populations. In the retina, small- to medium-sized perikarya in the inner nuclear layer, and small perikarya in the ganglion cell layer are ChAT-IR and AChE positive. The entire inner plexiform layer is AChE positive, while only sublaminae 1, 2 and 4 are ChAT-IR. No indication of cholinergic activity was observed in the optic axon layer.In the pineal organ, ChAT-IR is restricted to small perikarya situated rostrally and dorsally in the pineal end-vesicle. AChE-positive neurons are present throughout the pineal end-vesicle and the pineal stalk. The pineal tract (the pinealofugally projecting axons of intrapineal neurons) is strongly AChE positive, but displays no ChAT-IR. The distribution of pinealofugally projecting neurons, labeled with retrogradely transported HRP, is markedly dissimilar to that of the ChAT-IR elements. It is proposed that the photosensory pineal organ transmits photic information to the brain via a non-cholinergic pathway. The possibility that the ChAT-IR neurons represent small local interneurons is discussed in the light of comparative physiological and anatomical findings.     

Endogenous Dopamine Maintains Synchronous Oscillation of Intracellular Calcium in Primary Cultured-Mouse Midbrain Neurons

We demonstrated synchronous oscillation of intracellular Ca2+ in cultured-mouse mid-brain neurons. This synchronous oscillation was thought to result from spontaneous and synchronous neural bursts in a synaptic neural network. We also examined the role of endogenous dopamine in neural networks showing synchronous oscillation. Immunocytochemical study revealed a few tyrosine hydroxylase (TH)-positive dopaminergic neurons, and that cultured neurons expressed synaptophysin and synapsin I. Western blot analyses comfirmed synaptophysin, TH, and 2 types of dopamine receptor (DR), D1R and D2R expression. The synchronous oscillation in midbrain neurons was abolished by the application of R(-)-2-amino-5-phosphonopentanoic acid (AP-5) as an N-methyl-D-aspartate receptor (NMDAR) antagonist. This result suggests that the synchronous oscillation in midbrain neurons requires glutamatergic transmissions, as was the case in previously reported cortical neurons. SCH-12679, a D1R antagonist, inhibited synchronous oscillation in midbrain neurons, while raclopride, a D2R antagonist, induced a transient increase of intracellular Ca2+ and inhibited synchronous oscillation. We consider that endogenous dopamine maintains synchronous oscillation of intracellular Ca2+ through D1R and D2R, and that these DRs regulate intracellular Ca2+in distinctly different ways. Synchronous oscillation of midbrain neurons would be a useful tool for in vitro researches into various neural disorders directly or indirectly caused by dopaminergic neurons.     

Differential Effects of Chemical Sympathectomy on Expression and Activity of Tyrosine Hydroxylase and Levels of Catecholamines and DOPA in Peripheral Tissues of Rats

Tyrosine hydroxylase (TH) mRNA and activity and concentrations of 3,4-dihydroxyphenylalanine (DOPA) and catecholamines were examined as markers of sympathetic innervation and catecholamine synthesis in peripheral tissues of sympathectomized and intact rats. Chemical sympathectomy with 6-hydroxydopamine (6-OHDA) markedly decreased norepinephrine and to a generally lesser extent TH activities and dopamine in most peripheral tissues (stomach, lung, testis, duodenum, pancreas, salivary gland, spleen, heart, kidney, thymus). Superior cervical ganglia, adrenals and descending aorta were unaffected and vas deferens showed a large 92% decrease in norepinephrine, but only a small 38% decrease in TH activity after 6-OHDA. Presence of chromaffin cells or neuronal cell bodies in these latter tissues, indicated by consistent expression of TH mRNA, explained the relative resistance of these tissues to 6-OHDA. Stomach also showed consistent expression of TH mRNA before, but not after 6-OHDA, suggesting that catecholamine synthesizing cells in gastric tissue are sensitive to the toxic effects of 6-OHDA. Tissue concentrations of DOPA were mainly unaffected by 6-OHDA, indicating that much of the DOPA in peripheral tissues is synthesized independently of local TH or sympathetic innervation. The differential effects of chemical sympathectomy on tissue catecholamines, DOPA, TH mRNA and TH activity demonstrate that these variables are not simple markers of sympathetic innervation or catecholamine synthesis. Other factors, including presence of neuronal cell bodies, parenchymal chromaffin cells, non-neuronal sites of catecholamine synthesis and alternative sources of tissue DOPA, must also be considered when tissue catecholamines, DOPA and TH are examined as markers of sympathetic innervation and local catecholamine synthesis.     

D1 Dopamine Receptor Binding and mRNA Levels Are Not Altered After Neonatal 6-Hydroxydopamine Treatment: Evidence Against Dopamine-Mediated Induction of D1 Dopamine Receptors During Postnatal Development

Abstract: The role of dopaminergic innervation on the postnatal developmental expression of D₁ dopamine receptors was investigated. Bilateral destruction of dopa-mine-containing neurons was achieved by treating rats intracisternally with 6-hydroxydopamine (6-OHDA) on postnatal day 3, and rats were killed on day 21. To ensure effective reduction of D₁ receptor activation by residual dopamine, a group of 6-OHDA-lesioned rats was given twice daily injections of the D₁ receptor antagonist SCH-23390, from day 4 to 20. D₁ dopamine receptor binding was assessed in the caudate—putamen, nucleus accumbens, and olfactory tubercle by quantitative autoradiographic analysis of [³H]SCH-23390 binding. In addition, the relative amount of D_1A receptor mRNA was assessed by in situ hybridization of a ³⁵S-labeled riboprobe. In the developing rats, neither the amount of [³H]SCH-23390 binding nor the amount of D_1A receptor mRNA was altered by 6-OHDA lesioning followed by chronic treatment with SCH-23390. Thus, bilateral destruction of dopamine-containing neurons and treatment with SCH-23390 in neonatal rats did not interfere with the developmental expression of D₁ receptors or alter the levels of mRNA that code for this receptor protein. Treatment of intact rats with SCH-23390 from postnatal day 4 to 20 also did not alter [³H]SCH-23390 binding or levels of D₁ receptor mRNA. However, adult rats treated chronically with SCH-23390 exhibited increased [³H]SCH-23390 binding but did not show a significant change in D₁ receptor mRNA levels.     

MIF-1 fails to modify agonist-induced oral activity in neonatal 6-OHDA-treated rats

-Prolyl- -leucyl-glycinamide (MIF-1) is known to attenuate apomorphine-induced stereotypies in adult rats that are lesioned as neonates with 6-hydroxydopamine (6-OHDA). To test whether MIF-1 would affect dopamine (DA) agonist-induced and serotonin (5-HT) agonist-induced oral activity, both intact and neonatal 6-OHDA-treated rats were studied. Rats at 3 days from birth were injected with desipramine (20 mg/kg, IP), 1 h before 6-OHDA HBr (100 μg, salt form, in each lateral ventricle) or its vehicle, saline-ascorbic acid (0.1%). At approximately 6 months rats were treated with MIF-1 (0.1, 1.0, or 10.0 mg/kg, IP), 10 min before SKF 39393 HCl (1.0 mg/kg, IP) or m-chlorophenylpiperazine 2HCl (m-CPP 2HCl; 0.5 mg/kg, IP), DA D₁ and 5-HT_1C,2 receptor agonists, respectively. Although both agonists increased oral activity in control and neonatal 6-OHDA-treated rats, MIF-1 did not modify the response. In rats that received either of the three doses of MIF-1 for 21 consecutive days, there was still no observed effect of MIF-1 on the oral response of control and 6-OHDA-lesioned rats to SKF 38393 and m-CPP. These findings indicate that MIF-1 does not modify the oral activity response of supersensitized D₁ and 5-HT_1C receptors in adult rats that are lesioned neonatally with 6-OHDA.     

帕金森病模型大鼠脑内多巴胺与铁含量的关系

实验采用原子吸收分光光度法,快速周期伏安法,高效液相电化学检测等方法,研究以6－羟基多巴（6－OHDA）制备的帕金森病（PD）模型大鼠黑质内铁含量的变化。铁对多巴胺（DA）能神经元的直接毒性作用以及铁离子螯合剂甲磺酸去铁胺的神经保护作用。结果发现：（1）PD大鼠损毁侧黑质内铁含量为非标准PD大鼠的3倍左右;（2）PD大鼠损毁侧纹状体内铁含量无明显改变;（3）单纯注射6－OHDA的大鼠其损毁侧纹状体（CPu)DA的释放量和含量均明显降低;（4）侧脑室预先注射甲磺酸去铁胺,再重复上述实验,损毁侧CPu DA释放量和含量均无明显改变;（5）单侧黑质内注射40ug FeCl3后,大鼠损毁侧CPu内DA释放量和含量显著降低。上述结果提示,6－OHDA可导致CPu DA释放量及含量减少,此过程有铁的参与。由于铁可导致DA神经元死亡,因此铁含量的增加可能是DA含量减少的原因之一,甲磺酸去铁胺具有保护DA神经元的作用。     

Glucocorticoid Regulation of Motoneuronal Parameters in Rats with Spinal Cord Injury

1.Glucocorticoids exert beneficial effects after acute CNS injury in humans and experimental animals. To elucidate potential mechanisms of glucocorticoid action in the lesioned spinal cord, we have studied if treatment with dexamethasone (DEX) modulated the neurotrophin binding receptor p75 (p75^NTR) and choline acetyltransferase (ChAT), a marker of neuronal functional viability.2.Rats with a sham operation or with spinal cord transection at the thoracic level received vehicle or DEX several times postlesion and were sacrificed 48 hr after surgery. The lumbar region caudal to the lesion was processed for p75^NTR and ChAT immunoreactivity (IR) using quantitative densitometric analysis.3.We observed that p75^NTR-IR was absent from ventral horn motoneurons of sham-operated rats, in contrast to strong staining of neuronal perikaryon in TRX rats. Administration of DEX to TRX rats had no effect on the number of neuronal cell bodies expressing p75^NTR-IR but significantly increased the number and length of immunostained neuronal processes.4.Furthermore, spinal cord transection reduced ChAT immunostaining of motoneurons by 50%, whereas DEX treatment reverted this pattern to cells with a strong immunoreaction intensity in perikaryon and cell processes.5.It is hypothesized that increased expression of p75^NTR in cell processes and of ChAT in motoneurons may be part of a mechanism by which glucocorticoids afford neuroprotection, in addition to their known antiinflammatory effects.     

Ciliary neurotrophic factor induces cholinergic differentiation of rat sympathetic neurons in culture

Ciliary neurotrophic factor (CNTF) influences the levels of choline acetyltransferase (ChAT) and tyrosine hydroxylase (TH) in cultures of dissociated sympathetic neurons from newborn rats. In the presence of CNTF both the total and specific activity of ChAT was increased 7 d after culture by 15- and 18-fold, respectively, as compared to cultures kept in the absence of CNTF. Between 3 and 21 d in culture in the presence of CNTF the total ChAT activity increased by a factor of greater than 100. Immunotitration demonstrated that the elevated ChAT levels were due to an increased number of enzyme molecules. In contrast to the increase in ChAT levels, the total and specific activity levels of TH were decreased by 42 and 36%, respectively, after 7 d in culture. Half-maximal effects for both ChAT increase and TH decrease were obtained at CNTF concentrations of approximately 0.6 ng and maximal levels were reached at 1 ng of CNTF per milliliter of medium. The effect of CNTF on TH and ChAT levels were seen in serum-containing medium as well as in serum-free medium. CNTF was shown to have only a small effect on the long-term survival of rat sympathetic neurons. We therefore concluded that the effects of CNTF on ChAT and TH are not due to selective survival of cells that acquire cholinergic traits in vitro, but are rather due to the induction of cholinergic differentiation of noradrenergic sympathetic neurons.     

Effect of Ethanol Administration on Striatal D1 and D2 Dopamine Receptors

Chronic in vivo exposure of rats to ethanol in a complete liquid diet for 14 or 21 days produced a behavioral tolerance to the acute injection of ethanol. After 21 days, but not 14 days, of chronic exposure, there was a significant increase in the maximum density of striatal D1 and D2 dopamine receptors without a change in these receptors' affinities. A 24-h withdrawal from the 21-day exposure did not alter the observed increase in density. Both the level and duration of ethanol exposure appear to be important variables for demonstration of an increase in striatal D1 and D2 dopamine receptors.     

6-羟基多巴胺损毁大鼠内侧前脑束早期黑质-纹状体系统的铁水平与多巴胺能神经元退变的关系

应用快速周期伏安法(fast cyclic vohammetry,FCV)、原子吸收分光光度法及免疫组织化学方法,观察了6-羟基多巴胺(6-hydroxydopamine,6-OHDA)单侧损毁大鼠内侧前脑束(medial forebrain bundle,MFB)早期黑质(sub-stantia nigra,sN)铁水平与多巴胺(dopamine,DA)神经元损伤的变化,以及纹状体(striatum,Str)的DA释放。结果如下：6-OHDA单侧损毁大鼠MFB1d和3d后,SN的酪氨酸羟化酶(tyrosine hydroxylase,TH)阳性细胞分别下降了45％和66％;与正常鼠和未损毁侧相比,损毁侧SN的铁染色增强,铁浓度增加,而Str的DA释放量不变;6-OHDA损毁后1d与3d组相比,损毁侧的铁染色、铁浓度及DA释放量差别无显著性。上述结果表明,6-OHDA单侧损毁大鼠MFB的早期阶段,SN的DA能神经元数目中等程度减少时,铁染色及铁浓度即有增加,由于DA能神经系统有强大的代偿功能,使得Str的DA释放量仍趋于正常。     

阿片成瘾与中脑边缘DA系统的适应性变化

中脑－边缘ＤＡ神经阿片奖赏效应中起着关键性作用。长期应用阿片类药物可引起该系统靶神经元独特的适应性改变。主要包括：（１）中脑腹侧被盖区（ＶＴＡ）的ＴＨ被诱导增加、ＧｌｕＲ１受体上调、神经纤维丝蛋白的减少以及ＤＡ神经元的形态萎缩等；（２）伏核（ＮＡｃ）ＤＡＤ１受体超敏、Ｇｉ／ｏα亚单位的减少，ｃＡＭｐ－ＰＫＡ系统活性上调以及ｃＡＭＰ反应元蛋白（ＣＲＥＢ）和ｃ－ｆｏｓ、ｃ－ｊｕｎ基因表达的改变等。阿片     

Orexin A in the ventral tegmental area induces conditioned place preference in a dose-dependent manner: Involvement of D1/D2 receptors in the nucleus accumbens

It has been shown that orexin A in the ventral tegmental area (VTA) is necessary for development of morphine place preference. Additionally, D1 and D2 dopamine receptors in the nucleus accumbens (NAc) have critical roles in motivation and reward. However, little is known about the function of orexin in conditioned place preference (CPP) in rats and involvement of D1/D2 receptors in the NAc. In the present study, we investigated the effect of direct administration of orexin A into the VTA, and examined the role of intra-accumbal dopamine receptors in development (acquisition) of reward-related behaviors in the rats. Adult male Wistar rats were unilaterally implanted by two separate cannulae into the VTA and NAc. The CPP paradigm was used, and, conditioning score and locomotor activity were recorded by Ethovision software. The results showed that unilateral intra-VTA administration of orexin A (27, 53 and 107ng/0.3μl saline) during conditioning phase induced CPP in a dose-dependent manner. The most effective dose of intra-VTA orexin-A in eliciting CPP was 107ng. However, intra-NAc administration of SCH 23390 (0.25, 1 and 4μg/0.5μl saline), a D1 receptor antagonist, and sulpiride (0.25, 1 and 4μg/0.5μl DMSO), a D2 receptor antagonist, inhibited the development of orexin-induced CPP. The inhibitory effect of D2 but not D1 receptor antagonist was exerted in a dose-dependent manner. It is supposed that the activation of VTA dopaminergic neuron by orexin impresses the D2 receptors more than D1 receptors in the NAc.     

6-OHDA制备的帕金森病大鼠黑质神经元的超微结构改变

目的观察6-羟多巴胺(6-OHDA)单侧注射制备的帕金森病(PD)大鼠多巴胺(DA)能神经元的超微结构改变。方法单侧微量注射6-OHDA制备PD大鼠模型,用免疫荧光组织化学方法观察正常侧与6-OHDA注射侧黑质酪氨酸羟化酶(TH)阳性神经细胞及神经纤维的变化;并利用免疫电镜技术观察大鼠正常侧与注射侧黑质致密部DA能神经元的超微结构。结果免疫荧光法显示注射侧黑质致密部TH阳性细胞数和网状部TH阳性纤维面积与正常侧的百分比平均值分别为21.83%,23.19%。免疫电镜显示:TH免疫反应阳性产物表达于PD大鼠正常侧DA能神经元的高尔基复合体质膜面及胞质内,电子密度较高,注射侧很少见或几乎未见,且注射侧线粒体嵴有不同程度的溶解,呈空泡样变或髓样变,粗面内质网脱颗粒。结论6-OHDA可引起DA能神经元发生凋亡的超微结构改变。     

Role of Neostriatal Dopamine D1 and D2 Receptors in the Organization of Neuronal Activity in the Entopeduncular Nucleus

In chronic experiments on cats, we studied the effects of selective blockade of the dopamine D1 and D2 receptors in the nucleus caudatus (NC) against the background neuronal activity (BA) in the entopeduncular nucleus (ENT) and on the responses of these neurons evoked by stimulation of the subthalamic nucleus (STN). A blocker of D1 receptors, SCH 23390, and sulpiride, a blocker of D2 receptors, when injected into the NC head, led to changes in the BA frequency. The direction of these effects was different: blockade of the D2 receptors evoked a significant decrease in the BA frequency of ENT neurons, but when the D2 receptors were blocked, a trend toward an increase in this frequency was observed. Some of the ENT cells demonstrated similar changes in the temporal organization of their impulse activity with blockade of the D1 and D2 receptors. Namely, besides single action potentials (AP), high-frequency burst discharges began to be generated. Blockade of both D1 and D2 receptors prolonged the responses of ENT neurons to STN stimulation due to the appearance of similar AP bursts, while control animals demonstrated reactions consisting of solely single AP. The question on a dual (synergic and antagonistic) involvement of the neostriatal D1 and D2 receptors in the dopaminergic regulation of the basal ganglia is under discussion.     

Neonatal 6-Hydroxydopamine and Adult SKF 38393 Treatments Alter Dopamine D1 Receptor mRNA Levels: Absence of Other Neurochemical Associations with the Enhanced Behavioral Responses of Lesioned Rats

Abstract: To study potential biochemical correlates of dopamine (DA) and serotonin receptor supersensitivity, rats were lesioned at 3 days after birth with 6-hydroxydopamine (6-OHDA; 67 µg in each lateral ventricle; desipramine pretreatment, 20 mg/kg i.p., 1 h) and then sensitized with the DA D₁ agonist, SKF 38393 HCl (3.0 mg/kg i.p. per day) either ontogenetically (daily, for 28 consecutive days from birth) and/or in adulthood (four weekly injections, 6–9 weeks from birth). Controls received vehicle in place of 6-OHDA or SKF 38393. Enhanced locomotor responses were observed after SKF 38393 at 6 weeks, only in rats that received SKF 38393 + 6-OHDA in ontogeny. Locomotor responses were further enhanced in this group after the last of four weekly SKF 38393 injections at the 9th week. These weekly SKF 38393 treatments also produced enhanced responses in 6-OHDA rats that did not receive SKF 38393 in ontogeny. When striata were studied at 11 weeks, the percentages of high and low affinity DA D₁ binding sites were not altered. Basal as well as DA-, NaF-, and forskolin-stimulated adenylyl cyclase activities also were not changed. Dot blot analysis showed that there was a reduction of mRNA levels for DA D₁, but not serotonin_1C, receptors in the 6-OHDA groups. However, SKF 38393 at 6–9 weeks eliminated this alteration. Based on these findings it can be proposed that supersensitization may be a consequence of altered neuronal cross talk rather than an imbalance of receptor elements per se.     

Influence of alternating low frequency magnetic fields on reactivity of central dopamine receptors in neonatal 6-hydroxydopamine treated rats

The aim of this study was to evaluate the influence of extremely low frequency magnetic field (ELF MF) on the reactivity of the central dopamine D(1) receptor in rats with dopamine neurons chemically damaged by 6-hydroxydopamine (6-OHDA), an animal model of human's Parkinson's disease. The experiment was carried out on male Wistar rats. On day 3 of postnatal life, a lasting and selective chemical damage of the central dopamine system was induced in the rats by infusion of 6-OHDA HBr (133.4 microg intracerebroventricular, base form) given bilaterally into lateral ventricles of the brain. Control animals received similar treatments injecting only vehicle. At 2 months of age, both 6-OHDA treated and control rats were randomly divided into two groups. Rats from the first group were exposed to 10 Hz sinusoidal, 1.8-3.8 mT magnetic field one hour daily for 14 days. Rats of the second group were sham exposed, with the applicator solenoid turned off. On the day after the final exposure the evaluations were made of the rat's spontaneous irritability, oral activity, and catalepsy. The MF exposed rat with chemically induced dopamine neurons damage exhibited a reduction of irritability and oral activity when stimulated with SKF 38393 (the agonist of central dopamine D(1) receptor) and some increase of catalepsy after administration of SCH 23390(the antagonist of central dopamine D(1) receptor). These results indicate that ELF MF reduce the reactivity of central dopamine D(1) receptors in rats.     

Activation of nociceptin/orphanin FQ-NOP receptor system inhibits tyrosine hydroxylase phosphorylation, dopamine synthesis, and dopamine D(1) receptor signaling in rat nucleus accumbens and dorsal striatum

Nociceptin/orphanin FQ (N/OFQ) has been reported to inhibit dopamine (DA) release in basal ganglia mainly by acting on NOP receptors in substantia nigra and ventral tegmental area. We investigated whether N/OFQ could affect DA transmission by acting at either DA nerve endings or DA-targeted post-synaptic neurons. In synaptosomes of rat nucleus accumbens and striatum N/OFQ inhibited DA synthesis and tyrosine hydroxylase (TH) phosphorylation at Ser40 via NOP receptors coupled to inhibition of the cAMP/protein kinase A pathway. Immunofluorescence studies showed that N/OFQ preferentially inhibited phospho-Ser40-TH in nucleus accumbens shell and that in this subregion NOP receptors partly colocalized with either TH or DA D(1) receptor positive structures. In accumbens and striatum N/OFQ inhibited DA D(1) receptor-stimulated cAMP formation, but failed to affect either adenosine A(2A) or DA D(2) receptor regulation of cAMP. In accumbens slices, N/OFQ inhibited DA D(1)-induced phosphorylation of NMDA and alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate glutamate receptors, whereas in primary cultures of accumbal cells, which were found to coexpress NOP and DA D(1) receptors, N/OFQ curtailed DA D(1) receptor-induced cAMP-response element-binding protein phosphorylation. Thus, in accumbens and striatum N/OFQ exerts an inhibitory constraint on DA transmission by acting on either pre-synaptic NOP receptors inhibiting TH phosphorylation and DA synthesis or post-synaptic NOP receptors selectively down-regulating DA D(1) receptor signaling.     

Alterations in the cellular distribution of bcl-2, bcl-x and bax in the adult rat substantia nigra following striatal 6-hydroxydopamine lesions

The proteins of the bcl-2 family play an important role during apoptosis and may also regulate cell death in response to oxidative stress, which has been implicated in Parkinson's disease. In this study we examined the localization of the pro-apoptotic protein bax, and the anti-apoptotic proteins bcl-2 and bcl-x_L in the substantia nigra (SN) of the adult rat and their response to oxidative stress caused by striatal injections of 6-hydroxydopamine (6-OHDA). Our data show that bcl-2, bcl-x and bax proteins are present in the SN. Bcl-2 and bax are localized primarily in neurons including all those positive for tyrosine hydroxylase (TH). The intraneuronal distribution of bcl-2 and bax were different. Bcl-2 was diffuse throughout the cell while bax was localized in well-defined structures around the nucleus and within processes. Bcl-x staining in neurons was weak, though it was strongly expressed in GFAP-positive astrocytes. 6-OHDA injections, which resulted in loss of dopamine neurons between 7–14 days post-lesion, altered the distribution of bax, bcl-2 and bcl-x proteins in the SN. Bcl-2 and bax were decreased in the TH-positive cells of the SN from 3 to 14 days post-lesion and many TH-positive neurons were bcl-2 negative. Neuronal bcl-x was initially unchanged after lesion, but increased in astrocytes between 3–7 days post-lesion before the increase in GFAP immunoreactivity, which was detectable at days 10–14. While the neuronal distribution of bcl-2 and bcl-x does not change following lesion, bax became evenly distributed thought the soma. Morphological features of apoptosis, including TUNEL labeling and chromatin condensation was not observed. These data suggest that striatal 6-OHDA lesions do not result in classical apoptosis in the SN of the adult rat, even though there are changes in the content and distribution of members of the bcl-2 family of proteins.