Neuronal localization of the tyrosine-specific protein kinase p62c-yes in rat basal ganglia

The cellular localization of the tyrosine-specific protein kinase p62c-yes, the product of the proto-oncogene c-yes, has been examined in the striatonigral neurons which interconnect the rat neostriatum and substantia nigra. Although p62c-yes was more enriched in the neostriatum than in the substantia nigra, excitotoxin-induced necrosis of nerve cells in the neostriatum led to 50-60% decreases of p62c-yes both in the lesioned neostriatum and in the ipsilateral substantia nigra. Hence, the p62c-yes tyrosine kinase is present both in the cell body region and in the axonal and nerve terminal region of the striatonigral neurons. This localization indicates that the enzyme may be involved in both presynaptic and postsynaptic functions in mammalian forebrain neurons.

Quantitation of the levels of tyrosine hydroxylase and preproenkephalin mRNAs in nigrostriatal sites after 6-hydroxydopamine lesions

Expression of the striatal proenkephalin gene is modulated by dopaminergic input from the substantia nigra (SN). We have used rapid, specific and sensitive solution hybridization assays for the quantitation of tyrosine hydroxylase (TH) mRNA, preproenkephalin (PPenk) mRNA and total cellular RNA to compare ipsilateral and contralateral levels of these RNAs in tissue dissected from the origin and termination of the nigrostriatal pathway of individual rats following sham (vehicle) or 6-hydroxydopamine (6-OHDA) induced lesions of the SN. Three weeks after treatment the rats that had received 6-OHDA, but not sham treated controls, demonstrated a characteristic contralateral rotation in response to apomorphine. Four weeks after 6-OHDA treatment, TH mRNA levels were reduced below the limits of sensitivity of the assay (1 pg/ug RNA) in ipsilateral SN while the levels of TH mRNA in contralateral SN (4.8 pg/ug RNA) did not differ from that in sham treated animals. PPenk mRNA levels in striatum were increased 3 fold to 64.9 pg/ug RNA on the side of the 6-OHDA lesions while the contralateral PPenk mRNA levels (21.6 pg/ug RNA) did not differ from sham treatment. The 6-OHDA treatment did not alter the levels of total cellular RNA in either SN or striatum. These results provide quantitative evidence for the tonic inhibition of striatal proenkephalin gene expression by the dopaminergic nigrostriatal pathway.

The vigilance-promoting drug modafinil counteracts the reduction of tyrosine hydroxylase immunoreactivity and of dopamine stores in nigrostriatal dopamine neurons in the male rat after a partial transection of the dopamine pathway

We studied the ability of the vigilance-promoting drug modafinil to modulate the anterograde and retrograde changes in tyrosine hydroxylase (TH) immunoreactivity and in dopamine (DA) stores in the nigro-neostriatal DA neurons, following a partial hemitransection of this ascending DA system, using a combined morphometrical, biochemical and behavioural analysis. Modafinil was given daily i.p. in doses of 10-100 mg/kg, starting 15 min after the lesion, and the partially hemitransected rats were killed 2 weeks later. Changes in TH-immunoreactive nerve cell bodies and nerve terminals induced by the partial hemitransection were studied in the substantia nigra and neostriatum in combination with image analysis. The substantia nigra and neostriatum were also subjected to biochemical analysis of DA, 3,4-dihydroxyphenylacetic acid and homovanillic acid levels. Modafinil treatment dose-dependently (10-100 mg/kg) counteracted the hemitransection-induced disappearance of nigral TH-immunoreactive nerve cell body profiles and neostriatal TH-immunoreactive nerve terminal profiles. A 2-week treatment with 100 mg/kg of modafinil also counteracted the hemitransection-induced depletion of DA stores in the neostriatum and the ventral midbrain. Moreover, the repeated daily treatment with modafinil (100 mg/kg) protected against the hemitransection-induced disappearance of striatal 5-hydroxytryptamine, 5-hydroxyindoleacetic acid and noradrenaline levels. Striatal DA function was analysed by studying apomorphine-induced (1 mg/kg, s.c.) ipsilateral rotational behaviour 4 and 11 days after the operation. A marked dose-dependent reduction of ipsilateral rotational behaviour was demonstrated after the daily modafinil treatment in the partially hemitransected rats. In another model involving unilateral nigral microinjections of 6-hydroxydopamine, acute (one single dose) modafinil (100 mg/kg) did not affect the contralateral rotational behaviour induced by apomorphine (0.05 mg/kg s.c.), when given 30 min before the apomorphine. Taken together, morphological, neurochemical and behavioural evidence has been obtained that anterograde and retrograde changes induced in the DA stores and TH immunoreactivity of the nigro-neostriatal DA neurons by a partial hemistransection are counteracted by modafinil in a dose dependent way with 100 mg/kg producing a significant protective action against impairment of DA transmission. The results of this study open up the possibility that modafinil may protect against the anterograde and retrograde degeneration of nigrostriatal DA neurons seen after mechanically induced injury.

Flunarizine induces a transient loss of tyrosine hydroxylase immunoreactivity in nigrostriatal neurons

Neurotoxic effects of flunarizine (Fz), a selective calcium channel blocker, on the nigrostriatal dopamine system was investigated. Systemic injections of Fz to mice resulted in a transient loss of tyrosine hydroxylase (TH) immunoreactive nigrostriatal neurons without cell loss. TH immunoreactivity in these neurons was greatly reduced as rapidly as one day after drug administration (regardless of dosage used) and thereafter recovered in both dose- and time-dependent manners. Such a novel neurotoxic action of Fz may constitute a morphological substrate for reversible drug-induced parkinsonian signs described in recent clinical case reports.

Sequential changes in activities of superoxide dismutase and catalase in brain regions and liver during (-)deprenyl infusion in male rats

A continuous s.c. infusion of (-)deprenyl in young male rats at a dose of 2.0 mg/kg/day for 1 week significantly increased total superoxide dismutase (SOD) activities due to increases in both Cu Zn-SOD and Mn-SOD activities in certain brain regions such as the substantia nitra and striatum, but not in the hippocampus or cerebellum, or in the liver. With continuing infusion, enzyme activities of SOD were further increased in the following weeks, reaching a plateau at 3 weeks. In some cerebral cortices the increase became significant at 3 weeks. In contrast to SOD activities, an increase in catalase (CAT) activity became significant only after 2 weeks of infusion, and only in the brain regions where SOD activities were increased earlier. The delay in the increase in CAT activity following deprenyl infusion suggests that this increased CAT activity is an adaptive response to the earlier increase in deprenyl-induced SOD activities rather than a direct effect of deprenyl on CAT activity, although the latter possibility cannot be excluded.

Tissue-specific alternative splicing of the first exon generates two types of mRNAs in human aromatic L-amino acid decarboxylase

Aromatic-L-amino-acid decarboxylase (AADC) is an enzyme that plays an essential role in synthesizing catecholamines and serotonin in neuronal and endocrine tissues. AADC has also been detected in other nonneuronal tissues including liver and kidney, although its physiological role in nonneuronal tissues has not yet been defined. Previously we have cloned a human AADC cDNA from a neuronal tissue (pheochromocytoma) [Ichinose, H., Kurosawa, Y., Titani, K., Fujita, K., & Nagatsu, T. (1989) Biochem. Biophys. Res. Commun. 164, 1024-1030] and the corresponding genomic DNA [Sumi-Ichinose, C., Ichinose, H., Takahashi, E., Hori, T., & Nagatsu, T. (1992) Biochemistry 31, 2229-2238]. Here we present isolation and characterization of AADC cDNA and genomic DNA from a nonneuronal tissue (human liver). The nonneuronal and neuronal AADC mRNAs differed only in the region corresponding to the untranslated first exon. The first exon for the nonneuronal-type mRNA was located 4.2 kilobases upstream to that for the neuronal-type mRNA and 22 kilobases from exon 2, to which it is spliced. Determination of the transcription initiation site indicated that the length of the nonneuronal-type exon 1 was 200 bp. A TATA box-like motif was located between positions -26 and -20 from the transcription initiation site. These results showed that an alternative usage of the first exon in the 5'-untranslated regions produces two types of mRNAs in AADC and suggested that alternative splicing would regulate the tissue-specific expression of AADC.

Dopa-decarboxylation in the striata of rats with unilateral substantia nigra lesions

The source and site of the DOPA decarboxylation to dopamine in Parkinson's disease (PD) and animal models of PD are controversial. Since most of aromatic L-amino acid decarboxylase (AADC) are lost along with the degenerating dopaminergic neurons, we addressed the possibility that other decarboxylases or a novel protein that is structurally different from AADC decarboxylate L-DOPA in the denervated striatum. Immunotitration of the extracts from the denervated striatum with AADC antibody showed that all activity can be attributed to AADC-immunoreactive protein. We then investigated if there are non-dopaminergic intrinsic striatal neurons that express AADC. No evidence of such neurons was noted by immunocytochemistry and in situ hybridization.

Nigral damage and dopaminergic hypofunction in mesencephalon-immunized guinea pigs

To support a potential role for immune mechanisms in the destruction of substantia nigra (SN) neurons, guinea pigs were immunized with bovine mesencephalon containing SN neurons. After immunization no clinical signs of basal ganglia dysfunction appeared. However, pathological examination revealed evidence of neuronal damage in the SN in 8 of 17 guinea pigs immunized with bovine mesencephalon. No nigral pathology was noted in animals immunized with spinal cord gray matter or Freund's adjuvant alone. Accompanying the SN damage in mesencephalon-immunized guinea pigs was a 25% decrease in tyrosine hydroxylase activity in the SN and a 27% decrease in dopamine content in the striatum. Deposits of IgG were detected by immunohistochemical techniques in sections of SN from mesencephalon-immunized guinea pigs and in sections of human SN after exposure to serum from mesencephalon-immunized guinea pigs. These data document the antigenicity of SN and suggest the possibility that immune mechanisms can contribute to basal ganglia pathology.

Neurotensin increases tyrosine hydroxylase messenger RNA-positive neurons in substantia nigra after retrograde axonal transport

In previous studies we have shown that labelled neurotensin injected into the rat striatum was found to be transported retrogradely in dopaminergic neurons through a process which was receptor and microtubule dependent. Now, we show, by in situ hybridization, the consequences of the striatal injection of neurotensin on the gene expression of tyrosine hydroxylase in the substantia nigra. Rats were injected with neurotensin or its fragments in the striatum of one side and with saline or the inactive fragment on the other. The number of nigral cells expressing tyrosine hydroxylase mRNA was found to increase by 40% after injection of neurotensin or its active fragment (neurotensin 8-13). In the same experimental conditions, the inactive fragment (neurotensin 1-8) was without effect. Time-course experiments revealed that the tyrosine hydroxylase mRNA was increased 4 h after neurotensin injection but not at 1 or 16 h. The fact that the increase of mRNA parallels the appearance of labelled neurotensin in the substantia nigra indicates that the changes in the gene expression of tyrosine hydroxylase might be the consequence of the retrograde axonal transport of neurotensin. These results represent the first evidence for the existence of a long-distance retrograde signalling process in which the neuropeptide and presumably its receptor may serve as information molecule between synapses and the cell body.

Tyrosine hydroxylase-like (TH) immunoreactivity in Parkinson's disease and Alzheimer's disease

We used tyrosine hydroxylase immunoreactivity (TH) to mark dopaminergic fibers in cerebral tissue from adult persons with Parkinson's disease (PD) or Alzheimer's disease (AD). In the PD cases we found a loss of dopaminergic neurons in the ventral tegmental area (VTA), severely reduced TH fibers in dopaminergic terminal fields (particularly in the hippocampal perforant pathway) and neurofibrillary tangles (NFT), that occurred only in the perforant pathway. In contrast, AD cases were characterized by a lack of significant neuron loss in the VTA and by mild loss of TH fibers. A decreased dopaminergic innervation of the perforant pathway in cases of PD appears to be associated with the occurrence of NFT in these structures.

Membrane localization of endopeptidase-24.11 and peptidyl dipeptidase A (angiotensin converting enzyme) in the pig brain: a study using subcellular fractionation and electron microscopic immunocytochemistry

Brains from piglets were dissected and a block of tissue including the substantia nigra, globus pallidus, and entopeduncular nucleus was homogenized and then fractionated on discontinuous Percoll gradients. Ligand-binding assays using (-)-[3H]nicotine and [3H]quinuclidinyl benzilate served to delineate fractions containing nicotinic and muscarinic acetylcholine receptors. In this system endopeptidase-24.11 exhibited a biphasic distribution, consistent with its presence on both pre- and postsynaptic membranes. Peptidyl dipeptidase A (angiotensin converting enzyme; ACE) was associated with membrane fractions containing muscarinic receptors. An immunoblot of these fractions with an affinity-purified polyclonal antibody to ACE revealed only the neuronal form of ACE (Mr 170,000), the endothelial form (Mr 180,000) being undetectable. Electron microscopic immunoperoxidase staining of the substantia nigra, with an affinity-purified antibody to endopeptidase-24.11 at the preembedding stage, showed this antigen to be confined to the plasma membranes of boutons, axons, and some dendrites. Both pre- and postsynaptic membranes were stained, and occasionally other regions of the dendritic membrane were positive. No staining of synaptic vesicles within the boutons was observed. Thus, two independent approaches indicate that endopeptidase-24.11 is present on both pre- and postsynaptic membranes in the pig substantia nigra. The subcellular fractionation suggests that neuronal ACE is confined to dendritic membranes.

Chronic selegiline administration transiently decreases tyrosine hydroxylase activity and mRNA in the rat nigrostriatal pathway

Selegiline, a selective monoamine oxidase type B inhibitor, is beneficial in the treatment of Parkinson's disease. However, this beneficial effect is only transient, and patients must ultimately resort to treatment with standard levodopa therapy. We studied the effects of chronic selegiline treatment on the rat nigrostriatal pathway, to elucidate a neurochemical correlate for this adaptive clinical response. Selegiline treatment for 3, 7, 14, or 21 days decreased tyrosine hydroxylase (the enzyme that catalyzes the rate-limiting step in catecholamine biosynthesis) activity in the cell body regions (substantia nigra) of the nigrostriatal pathway. However, tyrosine hydroxylase activity measurements in the major terminal field region (corpus striatum) of the pathway did not correspond to those in the substantia nigra; in the corpus striatum, tyrosine hydroxylase activity was decreased at 3 and 7 days of treatment and recovered by 14 days. We tested whether the decrease in tyrosine hydroxylase activity was mediated by a decrease in tyrosine hydroxylase mRNA. Northern blot and RNA dot blot analyses (using a tyrosine hydroxylase-specific cDNA probe) of substantia nigra homogenates revealed a significant decrease in tyrosine hydroxylase mRNA at 3, 7, and 14 days of selegiline treatment, compared with controls. Conversely, after 21 days of selegiline, tyrosine hydroxylase mRNA levels were significantly higher (3-fold) than controls; this finding was not reflected in substantia nigra tyrosine hydroxylase activity. The 21-day increase in mRNA may be associated with the rebound in tyrosine hydroxylase activity observed in the corpus striatum. Thus, it is possible that the recovery in tyrosine hydroxylase activity in the corpus striatum is mediated through an increase in tyrosine hydroxylase protein transport from the substantia nigra to the corpus striatum and/or that the tyrosine hydroxylase enzyme exists in a more stabilized state during this period of time. These results demonstrate that monoamine oxidase type B-selective inhibitory doses of selegiline are capable of inducing transient decreases in tyrosine hydroxylase activity and tyrosine hydroxylase mRNA levels. Furthermore, these reversible effects may represent adaptive responses associated with pharmacological tolerance and the transient beneficial actions of this drug in Parkinson's disease.

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.

Mesencephalic dopaminergic cells exhibit increased density of neural cell adhesion molecule and polysialic acid during development

In the developing mesencephalon of the rat, the dopaminergic neurons are generated in the ventricular zone of the basal plate between E11 and E15 and then migrate along radial glia to the ventral surface of the developing mesencephalon. To study the factors that control migration and maturation of the dopaminergic neurons, we immunolabeled embryo and pups, ages E12-P21, for neural cell adhesion molecule (NCAM), polysialic acid (PSA) - a polysaccharide found in high amounts on NCAM during development, tyrosine hydroxylase (TH) - a marker of mesencephalic dopaminergic cells, and vimentin - the major cytoskeletal protein in radial glia in the rat. At E13, we noted that cells throughout the mesencephalon contained NCAM-immunoreactive (NCAM-IR) material but that cells along the ventral surface of the mesencephalon contained an increased amount of NCAM-IR material and PSA-immunoreactive (PSA-IR) material. At this age, we first noted a small number of TH-immunoreactive (TH-IR) cells adjacent to the marginal zone of the ventral surface of the mesencephalon. Many of the TH-IR cells contained an increased density of NCAM-IR material. At age E14, the pattern of increased density of NCAM-IR material on cells along the ventral surface of the mesencephalon persisted and a conspicuous amount of PSA-IR material was also noted on cells in this region. TH-IR cells were more numerous, and a striking number of the TH-IR cells also contained an increased amount of NCAM-IR material and PSA-IR material. With increasing age the distribution of NCAM-IR material and PSA-IR material in the mesencephalon became more uniform. Our work suggests that NCAM may be involved in control of migration and synthesis of TH in the dopaminergic cells of the developing mesencephalon.

Monoamine oxidases of the brains and livers of macaque and cercopithecus monkeys

We assessed the two forms of monoamine oxidase (MAO), MAO-A and MAO-B, in discrete regions of the brain and in cerebral micro- and macrovessels, choroid plexus, and liver of three species of monkeys: African Green, rhesus, and cynomolgus. MAO was determined by specific [3H]pargyline binding which is stoichiometric and irreversible and by measuring the rate of oxidation of several substrates. Cerebral micro- and macrovessels had low MAO content. Regional brain MAO did not vary by more than one-fold in the brains of each of the three species of monkeys and was higher in the basal ganglia than in the cerebral cortex or cerebellum. MAO in the choroid plexus was low, while the liver had higher MAO activity than any of the brain samples. The vast majority of MAO in all the tissues that we examined was of the MAO-B type, and specific [3H]pargyline binding correlated well with the oxidation rate of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine. These results show marked similarities in brain MAO distribution between monkey and man. Or the three monkey species, the African Green monkey had the lowest MAO activity in its cerebral microvessels, which constitute the blood-brain barrier, although the small number of observations in each group did not allow statistical analyses of the differences.

Mitochondrial function in Parkinson's disease. The Royal Kings and Queens Parkinson's Disease Research Group

There is increasing evidence for a defect of mitochondrial respiratory chain function in Parkinson's disease. Specific NADH CoQ1 reductase (complex I) deficiency has been identified in the substantia nigra. Available evidence suggests that this defect is confined to the substantia nigra and is not present elsewhere in the parkinsonian brain. The absence of a detectable mitochondrial abnormality in the substantia nigra of patients with multiple system atrophy also suggests that the complex I deficiency in Parkinson's disease is not simply due to an artifact of neuronal degeneration. Evidence for abnormal mitochondrial function in skeletal muscle is conflicting; two studies showed multiple respiratory chain defects and one study was unable to demonstrate any deficiency. A severe deficiency of complex I activity has been found in platelet mitochondria from parkinsonian patients. This finding has not as yet been confirmed. Platelet homogenates do not show the complex I deficiency, however, suggesting that such a preparation may be too insensitive to detect the defect. The role of complex I deficiency in the events that culminate in dopaminergic cell death in Parkinson's disease remains unresolved. It is likely that if this mitochondrial defect is confirmed, it will be related to a number of other factors, including environmental agents, oxidative stress, and genetic predisposition.

The ability of (-)deprenyl to increase superoxide dismutase activities in the rat is tissue and brain region selective

In a previous study we have shown that chronic administration of (-)deprenyl increases activities of superoxide dismutase (SOD) and catalase (CAT) in rat striatum (1). The present study attempted to clarify how specific the effect of deprenyl is to certain tissues and brain regions in the rat. Two mg/kg/day of deprenyl was continuously infused s.c. in young male Fischer-344 rats. On the 22nd day, rats were sacrificed and enzyme activities of SOD and CAT were determined in several different brain regions and the liver. Activities of both SOD and CAT were significantly increased in striatum and substantia nigra but not in hippocampus, cerebellum or liver. Both types of SOD (i.e. Cu Zn-SOD and Mn-SOD) were significantly increased in striatum, substantia nigra. Interestingly, in cerebral cortices of three different regions, activities also tended to increase (especially those of Mn-SOD), although the increase was not so striking as in substantia nigra and striatum. The results confirm the previous observation that (-)deprenyl can increase free radical scavenger enzyme activities in striatum and provide further evidence that this effect is selective to certain brain regions and tissue types.

Distribution of glutamic acid decarboxylase (Mr 67,000) in the basal ganglia of the rat: an immunohistochemical study with a selective cDNA-generated polyclonal antibody

Distinct isoforms of glutamic acid decarboxylase, the synthetic enzyme for GABA, exist in brain. Their distribution at the cellular level is not known, because previous studies have been confounded by the lack of monospecificity of available antibodies. We have examined the distribution of glutamic acid decarboxylase (Mr 67,000; GAD67) in the basal ganglia of the rat with a polyclonal antibody generated against the protein expressed in bacteria transformed with the corresponding cDNA. This antibody, which is directed against a portion of GAD67 non homologous to other known glutamic acid decarboxylase isoforms, selectively recognizes GAD67 on western blots. We show that GAD67 is present to various degree in all types of GABAergic neurons previously described in these regions. In contrast with results obtained with non-selective antibodies for glutamic acid decarboxylase, GAD67-positive neuronal cell bodies were readily detected in sections of the striatum, pallidum and substantia nigra in the absence of colchicine treatment. Modifications in the immunohistochemical procedure favoured staining of glutamic acid decarboxylase-positive fibres with the same antibody, indicating that GAD67 is also present in axon terminals of GABAergic neurons. The results suggest that GAD67 may be involved in GABA synthesis in both cell bodies and axon terminals of all GABAergic neurons of the basal ganglia, but is particularly abundant or accessible in their cell bodies.

Rescue of dying neurons: a new action for deprenyl in MPTP parkinsonism

Deprenyl slows the progression of disabling symptoms in Parkinson's disease (PD) by an unknown mechanism. It can block the action of MPTP on substantia nigra compacta (SNc) neurons by inhibiting monoamine oxidase B necessary to mediate the conversion of MPTP to MPP+, its active metabolite, in astroglia. Mice were pretreated with saline or the PD-producing toxin, MPTP (30 mg/kg) daily for 5 days and then after a further 3 days (to allow for the metabolism and excretion of the MPTP) were treated with deprenyl (0.25 or 10 mg/kg) or saline 3 times weekly for 20 days. In three series of mice treated with MPTP alone or MPTP-saline, serial sections through the SNc showed that averages of 37-42% of tyrosine hydroxylase (TH) immunoreactive neurons were lost gradually over 20 days. Joint counts of the numbers of TH-immunoreactive and Nissl-stained SNc somata from immediately adjacent sections established that the reductions in the numbers of TH-immunoreactive somata at 20 days after MPTP treatment represented neuronal death. Deprenyl treatment reduced the loss of TH-immunoreactive SNc neurons to averages of 14-16% for the 10-mg/kg and 0.25-mg/kg doses, respectively, and joint Nissl/TH counts for adjacent sections showed that reduction in the loss of TH-immunoreactive soma represented the rescue of SNc neurons that would have died by 20 days. The gradual loss of SNc neurons over the 20 days following MPTP exposure may reflect the toxin's axotomy-like effects on SNc neurons or the prolonged action of sequestered MPP+.(ABSTRACT TRUNCATED AT 250 WORDS)

Neurotoxic effects of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine in the substantia nigra and the locus coeruleus in BALB/c mice

The purpose of the present study was to determine whether 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), administered systemically or as a local infusion, has a direct neurotoxic action upon dopamine (DA) neurons in the substantia nigra (SN) and norepinephrine (NE) neurons in the locus coeruleus (LC) in BALB/c mice. Results indicated that both acute and repeated MPTP infusions (2 micrograms/0.3 microliter per side) significantly impaired locomotor activity, decreased stereotyped behavior and caused a disturbed pattern of locomotion in mice. The biochemical changes parallel the behavioral changes. Repeated MPTP infusions to the SN decreased DA levels markedly in the SN and the striatum; chronic MPTP infusions to the LC reduced NE levels markedly in the LC and the hippocampus. Furthermore, repeated MPTP injections for 7 days (30 mg/kg, one injection per day) have resulted in a long-lasting effect on both the nigral-striatal and the coeruleus-hippocampal systems. DA levels in the SN and the striatum were decreased at 1, 3, 7 and 28 days after the last MPTP injection. Similarly, NE levels in the LC and the hippocampus were also reduced markedly at the same time intervals examined. Behaviorally, repeated MPTP treatment also produced long-lasting motor deficits in mice at all time intervals studied. Moreover, the LC appeared to be more sensitive than the SN to the neurotoxic effects of MPTP. Immunohistochemical results have similarly revealed that repeated MPTP treatment markedly decreased tyrosine hydroxylase-positive cells and fibers in the SN and the LC. It also markedly decreased DA-beta-hydroxylase-positive cells and fibers in the LC.(ABSTRACT TRUNCATED AT 250 WORDS)

Cholinergic nigrotectal projections in the rat

In order to verify a possible target site of cholinergic neurons in the substantia nigra of the rat, a retrograde fiber tracing method was combined with choline acetyltransferase immunohistochemistry. After injection of WGA-HRP into the superior colliculus, approximately 12% of retrogradely labeled cells in the substantia nigra were found to express choline acetyltransferase immunoreactivity. These double labeled cells were located in the dorsal and lateral portions of the substantia nigra pars reticulata at its middle and caudal levels.

Double immunohistochemical detection of transmitter phenotype of proliferating cells using bromodeoxyuridine

We describe a new method that can determine transmitter phenotype of proliferating nerve cells at a given age. The procedure is based on indirect sequential double antigen immunofluorescence histochemistry for transmitter-synthesizing enzymes (glutamic acid decarboxylase and tyrosine hydroxylase) and the thymidine analogue, bromodeoxyuridine. The method permits simple, rapid, and effective anatomical detection, and promises to reduce certain limitations inherent in a combination with tritiated thymidine autoradiography. Employing this technique, we observed that many striatal cells expressing gamma-aminobutyric acid (GABA) and nigral cells expressing dopamine undergo the final mitosis at embryonic days 13-14 in the rat.

Gamma-aminobutyric acid (GABAB) receptor-mediated inhibition of tyrosine hydroxylase activity in the striatum of rat

The effects of GABA and GABA agonists on calcium and depolarization-dependent stimulation of tyrosine hydroxylase activity in striatal slices were studied. gamma-Aminobutyric acid and (-)baclofen inhibited, while muscimol and (+)baclofen did not affect, the stimulation of tyrosine hydroxylase. The inhibitory effect of GABA and (-)baclofen was blocked by the GABAB antagonist, phaclofen but not by the GABAA antagonist, picrotoxin. The data suggest that the activity of tyrosine hydroxylase on dopaminergic nigrostriatal terminals may be modulated by GABA via GABAB receptors.