Subpopulations of mesencephalic dopaminergic neurons express different levels of tyrosine hydroxylase messenger RNA.

Subpopulations of mesencephalic dopamine containing neurons possess different electrophysiological, pharmacological, biochemical, and anatomical properties. In order to determine whether such differences are related to the regulation of tyrosine hydroxylase, the rate limiting enzyme in the synthesis of catecholamines, the regional distribution of tyrosine hydroxylase messenger RNA in these neurons was examined using in situ hybridization histochemistry. In the mouse, labelling for tyrosine hydroxylase messenger RNA associated with individual neurons was significantly less in the lateral substantia nigra pars compacta than in the medial substantia nigra pars compacta and the ventral tegmental area. A similar pattern of labelling was observed in the rat. Labelling for tyrosine hydroxylase messenger RNA was significantly less in the lateral substantia nigra pars compacta than in medial pars compacta (a densely cellular region), the area dorsal to the medial substantia nigra pars compacta (a less cell dense region), and the ventral tegmental area. Differences in levels of labelling for messenger RNA in mesencephalic dopamine neurons were not related to differences in cell size as measured in sections processed for tyrosine hydroxylase immunohistochemistry. The results suggest that tyrosine hydroxylase messenger RNA is differentially regulated in subpopulations of mesencephalic dopamine neurons, supporting the view that these neurons are physiologically distinct.     

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.     

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.     

Basic FGF is present in dopaminergic neurons of the ventral midbrain of the rat.

Immunocytochemistry procedures and 6-hydroxy-dopamine-induced degeneration of dopamine nerve cells provided evidence that practically all tyrosine hydroxylase immunoreactive (IR) neurons of the substantia nigra and ventral tegmental area contain cytoplasmic basic fibroblast growth factor immunoreactivity (bFGF IR), while many astroglial cells in the neostriatum and substantia nigra contain nuclear bFGF IR. RNA blot analysis demonstrated strong expression of a major 3.7 kb bFGF mRNA in the substantia nigra and ventral tegmental area. These results indicate that bFGF may be a significant growth factor in the DA neurons.     

Adrenal medulla and substantia nigra co-grafts in peripheral nerve: chromaffin cells survive for long time periods and prevent degeneration of nigral neurons.

A series of degenerative cytoskeletal changes characterize grafts of embryonic substantia nigra when isolated for long time periods in the peripheral nervous system. This study was designed to determine whether the adrenal medulla could modulate the cytoskeletal changes in the substantia nigra when co-grafted within peripheral nerves. The sciatic nerves of young adult rats received single transplants of embryonic day 15 substantia nigra or co-transplants of substantia nigra plus young adult adrenal medulla in close proximity. Immunocytochemistry was used to examine the expression of tyrosine hydroxylase, phosphorylated (RT97) and non-phosphorylated (SMI-32) neurofilament proteins in the grafts. Single substantia nigra grafts, examined after 1 month, consisted of numerous neurons and fibers that expressed the epitope for tyrosine hydroxylase. Normal spatial distributions of the phosphorylated and non-phosphorylated neurofilament subunits were observed. In contrast, single 1-year-old nigral transplants were shrunken, contained significantly fewer tyrosine hydroxylase positive neurons and displayed abnormal neurofilaments staining patterns including swollen axons, a reduction in the density of labeled axons and perikaryal accumulation of the phosphorylated neurofilament subunit. When co-grafted with the adrenal medulla, the nigral transplants did not show the degenerative cytoskeletal aspects evident in the single 1-year-old grafts. The loss of neurons was prevented and the neurofilament immunolabeling was indistinguishable from the young substantia nigra preparations. In addition, all the 1-year-old adrenal medulla grafts were viable within the peripheral nerves, consisting of hundreds of cells identified by immunoreactivity to tyrosine hydroxylase and the rat beta-nerve growth factor receptor (192-IgG). The experiments illustrate a strong protective effect by the adrenal medulla on neurons of the substantia nigra in the peripheral nerve environment. It is suggested that a catecholaminergic trophic source and/or neural interactions with the adrenal medulla may be important factors in the long-term survival of neurons and maintenance of normal cytoskeletal characteristics in the grafted substantia nigra neurons under these experimental circumstances.     

Compartmental distribution of cytochrome oxidase in the striatum of the rat.

Endogenous cytochrome oxidase activity was investigated in the adult rat striatum at the light microscope level to see if it was distributed in accordance with the established striatal patch/matrix compartmentalisation. Striatal sections stained to visualise cytochrome oxidase activity were compared with serial sections stained to visualise tyrosine hydroxylase and calbindinD28k-like immunoreactivity, established markers of the matrix compartment. The distribution of endogenous cytochrome oxidase activity was found to coincide with the immunocytochemical staining pattern seen for tyrosine hydroxylase and calbindinD28k whereby areas of intense tyrosine hydroxylase and calbindinD28k-like immunoreactivity (termed the matrix) corresponded to areas of intense cytochrome oxidase activity. Conversely, areas of less intense tyrosine hydroxylase and calbindinD28k-like immunoreactivity (termed patches) corresponded to areas of low cytochrome oxidase activity. In addition, the distribution of two other oxidative enzymes involved in the regulation of mitochondrial respiration, succinic dehydrogenase and NADH-diaphorase, was examined in the striatum and substantia nigra by using histochemical techniques. Both NADH-diaphorase and succinic dehydrogenase histochemistry showed an uneven pattern of neuropil staining in the striatum. In the substantia nigra a few intensely stained cell bodies were seen in the dorsal-lateral tip of the pars reticulata with both histochemical techniques. By using an anti-cytochrome oxidase antibody an abundance of immunoreactive cell bodies and processes were seen in the substantia nigra, particularly in the dorso-medial rim and dorsal tip of the pars reticulata. The substantia nigra pars lateralis contained many intensely stained cytochrome oxidase-like immunoreactive cell bodies and processes.(ABSTRACT TRUNCATED AT 250 WORDS)     

Protective effects of kidney-tonifying Chinese herbal preparation on substantia nigra neurons in a mouse model of Parkinson’s disease

The Chinese herbs Herba Epimedii, Fructus Ligustri Lucidi and Rhizoma Polygonati were injected into Parkinson’s disease mice established via intraperitoneal injection of 1-methyl-4-phenyl-1, 2, 3, 6-tetrahydropyridine hydrochloride. The selective monoamine oxidase B inhibitor selegiline was used as a positive control drug. After successive administration for 4 weeks, Herba Epimedii could downregulate the expression of caspase-3 and increase the brain-derived neurotrophic factor level, as well as increase tyrosine hydroxylase activity in the substantia nigra of Parkinson’s disease mouse models. Rhizoma Polygonati could downregulate the expression of caspase-3 and FasL, and increase neural growth factor and brain-derived neurotrophic factor levels. Fructus Ligustri Lucidi could downregulate caspase-3 expression. Rhizoma Polygonati and Fructus Ligustri Lucidi did not produce obvious effects on tyrosine hydroxylase activity. Herba Epimedii and Fructus Ligustri Lucidi yielded similar effects on apoptosis-promoting factors to those elicited by selegiline. Herba Epimedii and Rhizoma Polygonati significantly increased the levels of neurotrophic factors compared with selegiline. Herba Epimedii significantly increased tyrosine hydroxylase activity compared with selegiline. It is indicated that the kidney-tonifying Chinese herbal preparation can downregulate the expression of apoptosis-promoting factors, increase neurotrophic factors levels in the substantia nigra and striatum, as well as increase tyrosine hydroxylase activity in the substantia nigra of Parkinson’s disease mouse models, thereby exerting a stronger or similar neuroprotective effects compared with selegiline.     

Dendrites of deep layer, somatosensory superior collicular neurons extend into the superficial laminae

Animals with 6-hydroxydopamine-induced partial unilateral lesions of the substantia nigra exhibit spontaneous recovery from motor asymmetry, a transitory increase in dopamine turnover and an increase in tyrosine hydroxylase activity in the denervated striatum. The recovery of function in these animals seems to be due to the compensatory increase in dopamine metabolism as well as due to the time-dependent increase in tyrosine hydroxylase resulting from either enzyme activation or following reinnervation of the denervated striatum by nigral efferents spared by the partial lesions.     

Spontaneous recovery from motor asymmetry in adult rats with 6-hydroxydopamine-induced partial lesions of the substantia nigra

Animals with 6-hydroxydopamine-induced partial unilateral lesions of the substantia nigra exhibit spontaneous recovery from motor asymmetry, a transitory increase in dopamine turnover and an increase in tyrosine hydroxylase activity in the denervated striatum. The recovery of function in these animals seems to be due to the compensatory increase in dopamine metabolism as well as due to the time-dependent increase in tyrosine hydroxylase resulting from either enzyme activation or following reinnervation of the denervated striatum by nigral efferents spared by the partial lesions.     

MPTP对褐鼠黑质NAPOR基因表达的影响

目的 研究腹腔注射1—甲基—4—苯基—1，2，3，6—四氢吡啶(MPTP)对褐鼠黑质神经母细胞瘤凋亡相关的RNA结合蛋白(NAPOR)基因表达的影响，为阐明帕金森病(PD)的分子机制提供线索。方法 通过腹腔注射MPTP建立褐鼠PD模型，采用逆转录PCR方法研究NAPOR在黑质的表达情况。结果 通过MPTP腹腔注射后褐鼠模型出现典型PD症状、黑质酪氨酸羟化酶表达水平明显降低验证PD模型成功，PD鼠黑质NAPOR基因表达明显上调。结论 NAPOR为RNA结合蛋白，其表达的模式与神经元凋亡密切相关。提示MPTP对黑质神经元的毒性可能通过改变NAPOR基因的表达，促进神经元凋亡而实现。     

Transient increase of brain derived neurotrophic factor mRNA expression in substantia nigra reticulata after partial lesion of the nigrostriatal dopaminergic pathway

By using non-isostopic in situ hybridization we have demonstrated a transient increase of BDNF mRNA in the lateral subregion of the substantia nigra pars reticulata 1 week after intrastriatal application of 6-OH-DA. These changes correlate with a partial reduction of dopamine (DA) content in the striatum but with a normal tyrosine hydroxylase immunoreactivity in substantia nigra pars compacta. Our data suggest that non-DA, BDNF expressing cells in substantia nigra pars reticulata may play a role in neuronal protection after partial lesions of the DA nigrostriatal pathway.     

Expression of ErbB4 in substantia nigra dopamine neurons of monkeys and humans

Abnormal neuregulin-1 signaling through its receptor (ErbB4) might be associated with schizophrenia, although their neuropathological contribution remains controversial. To assess the role of neuregulin-1 in the dopamine hypothesis of schizophrenia, we used in situ hybridization and immunoblotting to investigate the cellular distribution of ErbB4 mRNA in the substantia nigra of Japanese monkeys (Macaca fuscata) and human postmortem brains. In both monkeys and humans, significant signal for ErbB4 mRNA was detected in substantia nigra dopamine neurons, which were identified by melanin deposits. The expression of ErbB4 mRNA in nigral dopamine neurons was confirmed with an independent RNA probe, as well as with combined tyrosine hydroxylase immunostaining. Immunoblotting appeared to support the observation of in situ hybridization. Immunoreactivity for ErbB4 protein was much more enriched in substantia nigra pars compacta containing dopamine neurons than in neighboring substantia nigra pars reticulata. These observations suggest that ErbB4 is expressed in the dopaminergic neurons of primate substantia nigra and ErbB4 abnormality might contribute to the dopaminergic pathology associated with schizophrenia or other brain diseases.     

Verbascoside promotes the regeneration of tyrosine hydroxylase-immunoreactive neurons in the substantia nigra

Tyrosine hydroxylase is a key enzyme in dopamine biosynthesis. Change in tyrosine hydroxylase expression in the nigrostriatal system is closely related to the occurrence and development of Parkinson’s disease. Verbascoside, an extract from Radix Rehmanniae Praeparata has been shown to be clinically effective in treating Parkinson’s disease. However, the underlying mechanisms remain unclear. It is hypothesized that the effects of verbascoside on Parkinson’s disease are related to tyrosine hydroxylase expression change in the nigrostriatal system. Rat models of Parkinson’s disease were established and verbascoside (60 mg/kg) was administered intraperitoneally once a day. After 6 weeks of verbascoside treatment, rat rotational behavior was alleviated; tyrosine hydroxylase mRNA and protein expression and the number of tyrosine hydroxylase-immunoreactive neurons in the rat right substantia nigra were signiifcantly higher than the Parkinson’s model group. These ifndings suggest that the mechanism by which verbascoside treats Parkinson’s disease is related to the regeneration of tyrosine hy-droxylase-immunoreactive neurons in the substantia nigra.     

Relationship between the presence of dopaminergic neurons and GABA receptors in substantia nigra: Effects of lesions

Submaximal destruction of nigrostriatal dopaminergic projections resulted in a significant (25%) decrease in specific GABA binding in substantia nigra; under these conditions, striatal tyrosine hydroxylase activity was 15–44% of control. In rats with lesions which caused maximal destruction of nigrostriatal dopamine neurons (striatal tyrosine hydroxylase was less than 15% of control), specific GABA binding in substantia nigra was apparently not different from that obtained in intact controls. Two distinct processes may be occurring in response to the destruction of dopamine neurons: (1) the loss of GABA binding sites physically associated with nigral dopamine neurons; and (2) an increase in nigral GABA receptors associated with non-dopaminergic neurons. The latter process may result from a decrease in nigral GABA transmission secondary to the complete loss of dopaminergic synaptic activity in striatum.     

Chronic GM1 ganglioside treatment reduces dopamine cell body degeneration in the substantia nigra after unilateral hemitransection in rat

The effect of GM1 ganglioside on the recovery of dopaminergic nigro-striatal neurons was studied in rats after unilateral hemitransection. GM1 treatment partially prevented the decrease of tyrosine hydroxylase (TH) activity caused by hemitransection in the substantia nigra ipsilateral to the lesion. Concomitantly a significant increase of TH-immunoreactivity in the substantia nigra was also detected. In particular, chronic treatment with GM1 prevented the disappearance of TH-positive cell bodies in the substantia nigra and induced the appearance of longer TH-positive dendrites with respect to the saline treatment. These data indicate that GM1 treatment maintains the number of dopaminergic cell bodies in the substantia nigra after hemitransection by protecting against retrograde neuronal degeneration.     

Direct demonstration of interactions between substance P immunoreactive terminals and tyrosine hydroxylase immunoreactive neurons in the substantia nigra of the rat: an ultrastructural study

The results of many anatomical, physiological, and pharmacological studies suggest that substance P-containing neurons of the striatum project to the substantia nigra, and that substance P influences the activity of dopaminergic nigrostriatal neurons. The purpose of the present ultrastructural study was to employ dual immunocytochemical labeling to determine the morphological basis for the observed actions of substance P on nigral dopaminergic neurons. Substance P-like and tyrosine hydroxylase-like immunoreactivities were localized simultaneously at the ultrastructural level in the substantia nigra of the rat. A double label method was utilized which relied on a combination of the peroxidase-antiperoxidase method (Sternberger, 1979) for substance P, and immunogold or silver enhanced immunogold labeling for tyrosine hydroxylase. The present results indicate that tyrosine hydroxylase immunoreactive (THLI) dendrites in the substantia nigra receive synaptic input from terminals exhibiting substance P-like immunoreactivity. These findings support the idea that substance P is a major neurotransmitter in the striatonigral loop, and suggest that striatal substance P neurons act directly upon nigral dopaminergic cells.