Comparative distribution of mRNAs for glutamic acid decarboxylase, tyrosine hydroxylase, and tachykinins in the basal ganglia: an in situ hybridization study in the rodent brain

Neurotransmitter-related messenger RNAs were detected by in situ hybridization in sections of rat and mouse brains by using 35S-radiolabelled RNA probes transcribed from cDNAs cloned in SP6 promoter-containing vectors. The distribution of messenger RNAs for glutamic acid decarboxylase, tachykinins (substance P and K), and tyrosine hydroxylase was examined in the striatum, pallidum, and substantia nigra. Dense clusters of silver grains were observed with the RNA probe complementary of the cellular messenger RNA for glutamic acid decarboxylase (antisense RNA) over most large neurons in the substantia nigra pars reticulata and medium-sized to large neurons in all pallidal subdivisions. A few very densely and numerous lightly labelled medium-sized neurons were present in the striatum. Among the areas examined, only the striatum contained neurons labelled with the antisense tachykinin RNA. Most of these neurons were of medium size, and a few were large. With the antisense tyrosine hydroxylase RNA, silver grains were found over neurons of the substantia nigra pars compacta and adjacent A10 and A8 dopaminergic cell groups. No signal was observed with RNAs identical to the cellular messenger RNA for glutamic acid decarboxylase or tachykinin (sense RNA). These results show a good correlation with immunohistochemical studies, suggesting that documented differences in the distribution and the level of glutamic acid decarboxylase, tyrosine hydroxylase, and substance P immunoreactivities in neurons of the basal ganglia are related to differences in the level of expression of the corresponding genes rather than to translation accessibility, stability, or transport of the gene products.     

Glutathione depletion in rat brain does not cause nigrostriatal pathway degeneration

Summary Nigral cell death in Parkinson's disease (PD) may involve oxidative stress and mitochondrial dysfunction initiated by a decrease in reduced glutathione (GSH) levels in substantia nigra. L-buthionine-(S,R)-sulphoximine (BSO; 4.8 and 9.6 mg/kg/day), an irreversible inhibitor of -glutamyl cysteine synthetase, was chronically infused into the left lateral ventricle of rats over a period of 28 days and markedly reduced GSH concentrations in substantia nigra (approx. 59% and 65% in 4.8 and 9.6 mg/kg/d BSO respectively) and the striatum (approx. 63% and 80% in 4.8 and 9.6 mg/kg/d BSO respectively). However, the number of tyrosine hydroxylase (TH)-positive cells in substantia nigra was not altered by BSO-treatment compared to control animals. Similarly, there was no difference in specific [³H]-mazindol binding in the striatum and nucleus accumbens of BSO-treated rats compared to control rats. In conclusion, depletion of GSH following chronic administration of BSO in the rat brain does not cause damage to the nigrostriatal pathway and suggests that loss of GSH alone is not responsible for nigrostriatal damage in PD. Rather, GSH depletion may enhance the susceptibility of substantia nigra to destruction by endogenous or exogenous toxins.     

鱼藤酮致大鼠脑内α-突触核蛋白的表达分布变化

目的 研究鱼藤酮所致的帕金森病大鼠的脑内α-突触核蛋白（α—synuclein,ASN）分布。方法 Wistar大鼠随机分成两组,分别给予鱼藤酮和／或溶剂（对照组）皮下注射,4周后取脑组织,对黑质部位HE染色,光镜下观察Lewy小体形态;对黑质、海马、纹状体等脑区进行酪氨酸羟化酶（tyrosine hydroxylase,TH）、ASN免疫组织化学染色。结果 在对照组大鼠脑内,ASN广泛分布于各脑区,尤其在皮质、纹状体、海马等纤维投射丰富的区域。鱼藤酮处理的大鼠脑中,黑质TH阳性多巴胺能神经元数目减少、纹状体区TH阳性纤维脱失,黑质部位可见Lewy小体样结构;ASN阳性染色在各个脑区均有增强但各个脑区增强程度不一,黑质部位神经元胞浆和胞核内均有ASN明显聚集,纹状体可见ASN聚集围绕在细胞周围。海马部位偶见ASN在胞浆中点状聚集,胞核中无明显改变。结论 在鱼藤酮皮下注射导致的帕金森病大鼠的脑内,ASN在多个脑区中表达增加,而在黑质纹状体部位聚集最为明显,蛋白分布由多巴胺能神经元的突触末端向胞浆和胞核扩展。     

The GABA and substance P input to dopaminergic neurones in the substantia nigra of the rat.

In order to examine the synaptic input to dopaminergic neurones in the substantia nigra from GABAergic terminals and terminals that contain substance P, double and triple immunocytochemical studies were carried out at the light and electron microscopic levels in the rat. In a first series of experiments sections of the substantia nigra were incubated to reveal axon terminals containing either substance P or glutamate decarboxylase and then incubated to reveal dopaminergic neurones using tyrosine hydroxylase immunocytochemistry. Examination of this material in the light microscope revealed that many substance P- and glutamate decarboxylase-immunoreactive boutons were associated with the dopaminergic cells. In the electron microscope it was found that the perikarya and dendrites of the dopaminergic neurons received symmetrical synaptic input from terminals that displayed immunoreactivity for substance P or glutamate decarboxylase. A small proportion of the substance P-positive boutons formed asymmetrical synapses. In a second series of experiments sections of the substantia nigra were processed by the pre-embedding immunocytochemical technique for tyrosine hydroxylase and then the post-embedding immunogold technique for gamma-aminobutyric acid (GABA). Examination in the electron microscope revealed that the tyrosine hydroxylase-positive neurons received symmetrical synaptic input from many GABA-positive terminals. Quantitative analyses demonstrated that a minimum of 50-70% of all boutons afferent to the dopaminergic neurones display glutamate decarboxylase or GABA immunoreactivity. Triple immunocytochemical studies i.e. pre-embedding immunocytochemistry for tyrosine hydroxylase and substance P, combined with post-embedding immunogold staining for GABA, revealed that some of the substance P-immunoreactive boutons that were in contact with the dopaminergic neurones also displayed GABA immunoreactivity. In a third series of experiments the combination of anterograde transport of lectin-conjugated horseradish peroxidase or biocytin with post-embedding GABA immunocytochemistry demonstrated that at least one of the sources of GABA-containing terminals in the substantia nigra is the striatum. The results of the present study: (1) demonstrate that dopaminergic neurones in the substantia nigra receive symmetrical synaptic input from GABAergic and substance P-containing terminals, (2) show that a proportion of these terminals contain both substance P and GABA and (3) suggest that the major synaptic input to dopaminergic neurones is from GABAergic terminals and that a part of this innervation is derived from the striatum.     

Bilateral effects of unilateral GDNF administration on dopamine- and GABA-regulating proteins in the rat nigrostriatal system

Dopamine (DA) affects GABA neuronal function in the striatum and together these neurotransmitters play a large role in locomotor function. We recently reported that unilateral striatal administration of GDNF, a growth factor that has neurotrophic effects on DA neurons and enhances DA release, bilaterally increased striatal neuron activity related to locomotion in aged rats. We hypothesized that the GDNF enhancement of DA function and resulting bilateral enhancement of striatal neuronal activity was due to prolonged bilateral changes in DA- and GABA-regulating proteins. Therefore in these studies we assessed dopamine- and GABA-regulating proteins in the striatum and substantia nigra (SN) of 24 month old Fischer 344 rats, 30 days after a single unilateral striatal delivery of GDNF. The nigrostriatal proteins investigated were the DA transporter (DAT), tyrosine hydroxylase (TH), and TH phosphorylation and were examined by blot-immunolabeling. The striatal GABA neuron-related proteins were examined by assay of the DA D₁ receptor, DARPP-32, DARPP-32 Thr³⁴ phosphorylation, and glutamic acid decarboxylase (GAD). Bilateral effects of GDNF on TH and DAT occurred only in the SN, as 30 μg GDNF increased ser19 phosphorylation, and 100 μg GDNF decreased DAT and TH protein levels. GDNF also produced bilateral changes in GAD protein in the striatum. A decrease in DARPP-32 occurred in the ipsilateral striatum, while increased D₁ receptor and DARPP-32 phosphorylation occurred in the contralateral striatum. The 30 μg GDNF infusion into the lateral striatum was confined to the ipsilateral striatum and substantia nigra. Thus, long-lasting bilateral effects of GDNF on proteins regulating DA and GABA neuronal function likely alter physiological properties in neurons, some with bilateral projections, associated with locomotion. Enhanced nigrostriatal excitability and DA release by GDNF may trigger these bilateral effects.     

Axonal transport of proteins and glycoproteins in the rat nigro-striatal pathway and the effects of 6-hydroxydopamine

Following stereotaxic injection of [35S]methionine into the substantia nigra of adult rats, there was rapid local incorporation of radioactivity into acid-insoluble material. Incorporation peaked by 4 h and then decreased. In contrast, acid-precipitable radioactivity in the corpus striatum (the major projection site of the substantia nigra) rose markedly between 1 and 8 h followed by a plateau period and another even more marked increase between 24 h and 6 days. Experiments involving injection of [3H]fucose gave similar results except that most of the acid-precipitable radioactivity in the striatum appeared in an early wave. In each case radioactivity in the contralateral striatum was less than 11% of that on the ipsilateral side. Stereotaxic injection of colchicine (20 microgram) into the nigrostriatal pathway (within the median forebrain bundle) blocked transport of [35S]protein and [3H]glycoprotein by 90% and 50%, respectively. In animals treated with 6-hydroxydopamine (6-OHDA; treated neonatally or as adults) the accumulation of striatal [35S]protein was reduced to 7 to 26% of control levels; striatal [3H]glycoprotein was also reduced, but not as much (29% to 73% of control). In control experiments, [3H]DOPA wa injected into the substantia nigra, and [3H]dopamine was measured in corpus striatum; 6-OHDA treatment reduced the amounts of striatal [3H]dopamine recovered to 3% of control values. The failure of colchicine or 6-OHDA to block transport of incorporated fucose as effectively as the transport of incorporated methionine is possible due to greater diffusion of fucose away from the injection site to non-dopaminergic nuclei projecting to the striatum. The molecular weight distribution of radioactive proteins at the substantia nigra and corpus striatum was analyzed by polyacrylamide gel electrophoresis. For both [35S]methionine and [3H]fucose, the gel electrophoretic pattern of radioactive proteins in the injection site (substantia nigra) was complex and did not change greatly between 2 h and 6 days. At the projection site (striatum) the electrophoretic distribution pattern was initially different from that of the substantia nigra, and changed markedly over the course of several days. In 6-OHDA-treated animals (treated neonatally or as adults), the bulk of proteins transported in nigro-striatal non-dopaminergic neurons appears to be very similar to that transported in the intact pathway in control rats. However, in striata of 6-OHDA-treated animals, a consistent reduction in striatal 35S- and 3H-radioactivitiy was observed in proteins with molecular weight from about 67,000 to 77,000. Assuming that the 6-OHDA treatment did not substantially affect the non-dopaminergic neurons, we interpret this to mean that some of the proteins in this molecular weight range are transported primarily by dopaminergic neurons.     

Exposure to perinatal morphine promotes developmental changes in rat striatum

This study shows that perinatal exposure to morphine promotes developmental changes (up to 8 months of life) in the striatum by up-regulating concentrations of substance P and met-enkephalin with changes of prometenkephalin A mRNA expression at the day of birth only. Dopamine metabolism (up to 60 days) is also increased as suggested by the reduced concentrations of dopamine and increased content of 3,4-dihydroxyphenylacetic acid. Tyrosine hydroxylase mRNA expression is selectively reduced only in the substantia nigra by perinatal morphine. Serotonin content is reduced only during the early postnatal days and is unaffected thereafter. Supplementation of naltrexone to morphine-exposed rats prevents monoaminergic and neuropeptidergic changes in the striatum, which directly implicates opioid receptors in the developmental changes caused by morphine. The data suggest that perinatal morphine may inhibit met-enkephalin release, causing accumulation of the peptide without corresponding changes in specific mRNA. Dopamine release may also be increased as indicated by a higher metabolism and consequent reduction of tyrosine hydroxylase mRNA expression in the substantia nigra.     

In vivo synthesis of substance P in the corpus striatum of the rat and its transport to the substantia nigra

Incorporation of [³⁵S]methionine into substance P in the striatum of the rat and the subsequent transport of the labelled peptide to the substantia nigra has been demonstrated in vivo. After a 4-h infusion of [³⁵S]methionine into the corpus striatum and an additional interval of 4 h radiolabelled substance P was found in the striatum and the substantia nigra of the animals. The criteria for concluding that the labelled product was substance P were: (a) gel chromatography and subsequent ion exchange chromatography of an acetic acid extract of the infused striatum or the ipsilateral substantia nigra yielded a peak of radioactivity co-eluting with endogenous immunoreactive substance P or a sample of synthetic substance P; (b) the radioactive material from this peak also co-chromatographed with synthetic substance P on high-voltage paper electrophoresis or high-pressure liquid chromatography; and (c) bound specifically to the substance P antibody. Intracisternal injection of colchicine (70 μg, i.c.) completely suppressed the appearance of radiolabelled substance P immunoreactive material in the substantia nigra.The data indicate that synthesis of substance P occurs in nerve cell bodies located in the corpus striatum and that substance P is transported to the substantia nigra by a colchicine sensitive mechanism.     

Gene therapy of Parkinson's disease using adeno-associated virus (AAV) vectors

Parkinson's disease (PD) is characterized by the progressive loss of the dopaminergic neurons in the substantia nigra and a severe decrease in dopamine in the striatum. A promising approach to the gene therapy of PD is intrastriatal expression of dopamine-synthesizing enzymes [tyrosine hydroxylase (TH) and aromatic L-amino acid decarboxylase (AADC)]. The most appropriate gene-delivery vehicles for neurons are adeno-associated virus (AAV) vectors, which are derived from non-pathogenic virus. Therefore, TH and AADC genes were introduced into the striatum in the lesioned side using separate AAV vectors in parkinsonian rats, and the coexpression of TH and AADC resulted in better behavioral recovery compared with TH alone. Another strategy for gene therapy of PD is the protection of dopaminergic neurons in the substantia nigra using an AAV vector containing a glial cell line-derived neurotrophic factor (GDNF) gene. Combination of dopamine-supplement gene therapy and GDNF gene therapy would be a logical approach to the treatment of PD.     

Inhibition of striatal energy metabolism produces cell loss in the ipsilateral substantia nigra

This study examined whether damage to dopamine (DA) nerve terminals via inhibition of energy metabolism in the striatum would result in the retrograde loss of cell bodies in the substantia nigra. Infusion of 2 μmol malonate into the left striatum of rats resulted in a 67% loss of striatal DA and a 40% loss of tyrosine hydroxylase (TH)-positive neurons in the substantia nigra. No change in the number of Nissl-positive-TH-negative neurons was observed. These findings demonstrate the retrograde destruction of DA cell bodies in the substantia nigra resulting from energy impairment at their terminal projection site.     

Long-term striatal overexpression of GDNF selectively downregulates tyrosine hydroxylase in the intact nigrostriatal dopamine system

Sustained neurotrophic factor treatment in neurodegenerative disorders such as Parkinson's disease is likely to affect both degenerating and intact neurons. To investigate the effect of long-term glial cell line-derived neurotrophic factor (GDNF) overexpression on intact nigrostriatal dopamine neurons, we injected a recombinant lentiviral vector encoding GDNF, or green fluorescent protein, in the right striatum of young adult rats. Thirteen months after viral injection GDNF levels were 4.5 ng/mg tissue in the striatum and 0.9 ng/mg in the substantia nigra as measured by ELISA, representing a 25-100-fold increase above control vector- or nontransduced tissue. GDNF overexpression significantly reduced tyrosine hydroxylase mRNA levels (by 39-72%) in the substantia nigra and ventral tegmental area neurons, and the optical density of tyrosine hydroxylase-immunoreactive innervation in the striatum was reduced by 25-52% with the most prominent reductions appearing caudally. No significant reduction was seen in striatal vesicular monoamine transporter 2-immunoreactivity or [3H]mazindole binding autoradiography to dopamine uptake sites, two other presynaptic markers in dopamine axon terminals. The striatal D1 and D2 receptor binding as determined by [3H]SCH23390 and [3H]spiperone binding, respectively, was unaltered relative to the intact side in both treatment groups. Preproenkephalin mRNA levels in postsynaptic striatal neurons, which increase upon removal of striatal dopamine, were also unaffected by the GDNF treatment. Taken together our findings indicate that sustained GDNF administration to intact nigrostriatal dopamine neurons selectively reduces tyrosine hydroxylase expression, without altering striatal dopamine transmission to the extent that compensatory changes in several other components related to dopamine storage and signalling occur.     

Comparative distribution of messenger RNAs encoding glutamic acid decarboxylases (Mr 65,000 and Mr 67,000) in the basal ganglia of the rat.

Glutamic acid decarboxylase, the enzyme required for GABA synthesis, exists as distinct isoforms, which have recently been found to be encoded by different genes. The relative expression of messenger RNAs encoding two isoforms of glutamic acid decarboxylase (Mr 67,000 and Mr 65,000) was measured at the single-cell level in neurons of the rat basal ganglia with in situ hybridization histochemistry. Both messenger RNAs were expressed in neurons of the striatum, pallidum, and substantia nigra pars reticulata, but marked differences in the relative level of labelling were observed with the two probes. In striatum, efferent neurons were more densely labelled for the messenger RNA encoding glutamic acid decarboxylase (Mr 65,000) than for the messenger RNA encoding glutamic acid decarboxylase (Mr 67,000), whereas the reverse was observed for GABA-ergic interneurons. Neurons of the entopeduncular nucleus were much more densely labelled for messenger RNA encoding glutamic acid decarboxylase (Mr 65,000) than for messenger RNA encoding glutamic acid decarboxylase (Mr 67,000). In addition, labelling for messenger RNA encoding glutamic acid decarboxylase (Mr 65,000) was higher in the entopeduncular nucleus (internal pallidum) than in the globus pallidus (external pallidum), a structure which expressed similar levels of both mRNAs. In contrast to neurons of the internal pallidum, efferent neurons of the substantia nigra pars reticulata expressed slightly more messenger RNA encoding glutamic acid decarboxylase (Mr 67,000) than that encoding the other isoform of the enzyme. The results suggest a differential expression of the messenger RNAs encoding the two isoforms of glutamic acid decarboxylase in subpopulations of basal ganglia neurons in rats.     

Nerve growth factor (NGF) in the rat CNS: Absence of specific retrograde axonal transport and tyrosine hydroxylase induction in locus coeruleus and substantia nigra

Selective, highly efficient uptake of [125I]NGF by nerve terminals followed by retrograde axonal transport, and specific induction of tyrosine hydroxylase by NGF are well known phenomena in peripheral adrenergic neurons of adult rats. In the present study these parameters were used in order to detect possible interactions of NGF with central catecholaminergic neurons. No selective retrograde transport of [125I]NGF could be detected by light microscopic autoradiography from the caudate nucleus to the dopaminergic neurons in the substantia nigra or from the hippocampus to the noradrenergic nerve cells of the locus coeruleus. Biochemically, no change in tyrosine hydroxylase activity could be observed for up to 3 days after injection of either NGF, anti-NGF antibodies, or control proteins close to the nerve cell bodies in the substantia nigra or the locus coeruleus. These data suggest a fundamental difference between central and peripheral adrenergic neurons with regard to their responsiveness of NGF.     

Nitric oxide synthase inhibition and MPTP-induced toxicity in the common marmoset

Nitric oxide, produced following activation of N-methyl-D-aspartate (NMDA) receptors, may be involved in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) toxicity since NMDA receptor antagonists have been shown to prevent MPTP induced nigral cell loss in primates. Common marmosets were treated with either saline or MPTP or L-N^Gnitro arginine methyl ester (L-NAME) or MPTP and L-NAME. MPTP-treated common marmosets showed motor deficits including bradykinesia, rigidity, and tremor accompanied by a marked loss of tyrosine hydroxylase-immunoreactive neurones in the substantia nigra pars compacta and of [³H]-mazindol binding in the caudate-putamen. MPTP treatment also caused an increase in glial fibrillary acidic protein (GFAP) staining in the substantia nigra compared to controls. However, MPTP treatment did not alter the number of constitutive nitric oxide synthase-immunoreactive neurones in the caudate-putamen. Furthermore, neurones or glial cells immunoreactive for inducible nitric oxide synthase were not observed in the substantia nigra pars compacta following MPTP treatment. L-NAME treatment alone did not produce any behavioural changes in marmosets and did not alter the number of tyrosine hydroxylase-immunoreactive cells in the substantia nigra pars compacta, the number of constitutive nitric oxide synthase-immunoreactive neurones or [³H]-mazindol binding in the caudate-putamen compared to saline-treated control animals. Furthermore, L-NAME did not affect the motor deficits, loss of tyrosine hydroxylase-immunoreactive neurones in the substantia nigra pars compacta, loss of [³H]-mazindol binding in the caudate-putamen, or the increase in GFAP staining in the substantia nigra induced by MPTP treatment of common marmosets. The failure of L-NAME to protect against MPTP-induced toxicity in the marmoset suggests that nitric oxide does not play a major role in such toxicity and casts doubt over the involvement of the NMDA:nitric oxide system in neurodegeneration in MPTP-treated primates. Synapse 26:301–316, 1997. © 1997 Wiley-Liss, Inc.     

Dopaminergic neurons: Effect of acute and chronic morphine administration on single cell activity and transmitter metabolism

Summary At various time points following acute and chronic administration of morphine to rats, dopamine transmitter metabolism and neuronal activity were determined. Following acute injection of morphine (20 mg/kg intraperitoneally), dopamine cell firing rates increased slowly and steadily. This slow increase was accompanied by a similar slow increase in the accumulation of the dopamine metabolite, dihydroxyphenylacetic acid (DOPAC). Apparentin vivo tyrosine hydroxylase activity, measured by dopa accumulation following inhibition of dopa decarboxylase, also increased. In chronically treated animals the average firing rate of dopamine cells was measured two hours after the last injection of morphine. The distribution of dopamine cell firing rates was significantly higher than in controls. DOPAC levels andin vivo tyrosine hydroxylase activity were also increased at this time. When morphine (100 mg/kg intraperitoneally) was administered to chronically treated animals 12 hours after the last injection a slow increase of firing rates was observed similar to that seen in naive animals after an acute morphine injection. In chronically morphine treated animals naloxone caused a rapid dose-dependent decrease in firing rates and DOPAC levels.In vivo tyrosine hydroxylase activity was not changed.This work is derived in part from a dissertation presented to the Yale Graduate School by M. C. Nowycky in partial fulfillment of the requirements for the degree of Doctor of Philosophy and was performed during tenure of a United States Public Health Service Predoctoral Fellowship under Training Grant CA 09085.     

In vivo labelling and axonal transport of monoamine oxidase in the rat basal ganglia using radioactive pargyline

Summary The enzyme monoamine oxidase was labelled in the rat striatum or substantia nigra with locally injected radioactive pargyline. The binding was prevented by a pretreatment with non-radioactive pargyline, or with a combination of clorgyline and deprenyl. Most of the MAO labelled with³H-pargyline was of the B-type, but also some MAO-A was labelled, as shown in rats pretreated with clorgyline or deprenyl separately.Seven days after the injection of (³H)-pargyline into the striatum a significant labelling was observed in the substantia nigra. This labelling was clorgyline sensitive, indicating type A MAO, and was not present when striatal neurons were destroyed with kainic acid. Labelling of the striatum following³H-pargyline injection into the substantia nigra was also less in kainate intoxicated striata. Damage of nigral dopamine neurons with 6-hydroxydopamine did not influence the distribution of the label.Thus by using³H-pargyline, specific labelling and axonal transport of type A MAO in striatal neurons projecting to the substantia nigra was demonstrated.     

Decreased tyrosine hydroxylase content in the dopaminergic neurons of MPTP–intoxicated monkeys: Effect of levodopa and GM1 ganglioside therapy

Parkinson's disease is characterized by the degeneration of melanized dopaminergic neurons of the substantia nigra. The functional capacity of the surviving dopaminergic neurons is affected, as suggested by the subnormal levels of tyrosine hydroxylase messenger RNA and protein found in the remaining cells. The reduced expression of tyrosine hydroxylase may be due to either the evolving neurodegenerative process or its downregulation, possibly secondary to chronic levodopa treatment. The cellular content of tyrosine hydroxylase was determined in the mesencephalon from 16 Macaca fascicularis monkeys, using a semiquantitative immunocytochemical method. Thirteen monkeys were rendered parkinsonian by weekly intravenous injections of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) for 2 (subacute treatment) or 20 (chronic treatment) weeks. Three of the monkeys received levodopa and 3 others received GM1 ganglioside. The loss of dopaminergic neurons in the mesencephalon of the MPTP-intoxicated monkeys was severe in the substantia nigra, intermediate in cell groups A8 and A10, and almost undetectable in the central gray substance. After both subacute and chronic treatment, the cellular content of tyrosine hydroxylase was reduced by 40% in the surviving neurons of the lesioned substantia nigra, but by less in the other mesencephalic dopaminergic regions. Neuronal survival and tyrosine hydroxylase content in monkeys that had received levodopa were not significantly different. The cellular content of tyrosine hydroxylase was increased in the substantia nigra of the monkeys that received GM1 ganglioside injections. The results show that the decreased expression of tyrosine hydroxylase found in nigral dopaminergic neurons after partial degeneration of the mesostriatal dopaminergic system is not influenced by levodopa treatment and is partially reversed by GM1 ganglioside administration.     

Dissociation between the presynaptic dopamine-sensitive adenylate cyclase and [H]spiperone binding sites in rat substantia nigra

[3H]Spiperone binding sites and the dopamine-sensitive adenylate cyclase were measured in rat substantia nigra (s. nigra) 7 or 14 days after various lesions. Hemisections, which resulted in a 66% decline in tyrosine hydroxylase and cyclic nucleotide phosphodiesterase and a 73% decrease in glutamate decarboxylase, led to a 50% decrease in [3H]spiperone binding and to the almost complete disappearance of the dopamine-sensitive adenylate cyclase from the s. nigra on the lesioned side. 6-Hydroxydopamine injection into the s. nigra, which depleted tyrosine hydroxylase activity within the s. nigra by 85%, while leaving phosphodiesterase unaffected, resulted in a 40% decrease in [3H]spiperone binding but no change in the dopamine-sensitive adenylate cyclase. Intrastriatal injections of kainic acid did not alter tyrosine hydroxylase activity in the s. nigra, but decreased both glutamate decarboxylase (54%) and phosphodiesterase (68%); [3H]spiperone binding was unaffected by this lesion while the dopamine-sensitive adenylate cyclase was greatly reduced (50-75%). These results suggest that within the s. nigra the dopamine receptor binding sites as defined using [3H]spiperone are located on dopamine neurones while the dopamine-sensitive adenylate cyclase is located presynaptically on striatonigral nerve terminals.     

酪氨酸羟化酶cDNA移植治疗帕金森病的实验研究

帕金森病(PD)的主要病因是黑质多巴胺能神经元损伤,表达的酪氨酸羟化酶(TH)减少。本文在应用6-羟多巴胺(6-OHDA)制备偏侧PD大鼠模型的前提下,首次将TH cDNA移植到PD大鼠纹状体内,模型动物的旋转行为明显改善,用免疫组化法及PCR法证实了外源性THcDNA可以进入脑细胞内,并表达出有生物活性的TH。