An immunohistochemical study on alpha-ketoglutarate dehydrogenase complex in Parkinson's disease

We report an immunohistochemical study of the mitochondrial alpha-ketoglutarate dehydrogenase complex (KGDHC) in the substantia nigra in Parkinson's disease. The KGDHC, the three enzyme complex catalyzing the oxidation of alpha-ketoglutarate to succinate through succinic semialdehyde, is the rate-regulating enzyme of the TCA cycle. The mitochondrial toxin, MPP+, inhibits not only complex I but also the KGDHC. Therefore, we investigated this enzyme complex in Parkinson's disease. In the control patients (n = 6), the immunostaining of the melanized nigral neurons was generally uniform; most of the melanized neurons showed good immunostaining with some neurons showing somewhat reduced staining. In Parkinson's disease (n = 9), many melanized neurons showed reduced immunostaining for the KGDHC, and those neurons were more frequently seen in the lateral one-third of substantia nigra. The decrease in the immunostaining for the KGDHC correlated roughly with the severity of degeneration. The KGDHC is more vulnerable to degeneration than complex II, III, and IV as noted in our previous immunohistochemical study. Even if secondary, the loss may play a role in the progression of the disease.

Quantification of mRNA of tyrosine hydroxylase and aromatic L-amino acid decarboxylase in the substantia nigra in Parkinson's disease and schizophrenia

Using the reverse transcription-polymerase chain reaction (RT-PCR), we developed a sensitive and quantitative method to detect all four types of human tyrosine hydroxylase (TH) mRNAs in the human brain (substantia nigra). All four types of TH mRNAs were found in the substantia nigra in the control brains examined, and the ratio of type-1, type-2, type-3, and type-4 mRNAs to the total amount of TH was 45, 52, 1.4, and 2.1%, respectively. The average amount of total TH mRNA in the normal brain (substantia nigra) was 5.5 amol of TH mRNA per microgram of total RNA. The ratios of four TH isoforms were not altered significantly in Parkinson's disease or schizophrenia. Further we measured the relative amount of aromatic L-amino acid decarboxylase (AADC) and beta-actin mRNAs in the brain samples. TH and AADC mRNAs were highly correlated in the control cases. We found that parkinsonian brains had very low levels of all four TH isoforms and AADC mRNAs in the substantia nigra compared with control brains, while no significant differences were found between schizophrenic brains and normal ones. Since the decrease in AADC mRNA was comparable to that in TH mRNA, the alteration of TH in Parkinson's disease would not be a primary event, but it would reflect the degeneration of dopaminergic neurons in the substantia nigra. This is the first reported measurement of mRNA contents of TH isoforms and AADC in Parkinson's disease and schizophrenia.

Haloperidol activates tyrosine hydroxylase gene-expression in the rat substantia nigra, pars reticulata

The cellular distribution of tyrosine hydroxylase (TH) and TH mRNA in the rat substantia nigra (SN) was investigated using immunohistochemistry (IMHC) and non-radioactive in situ hybridization histochemistry (ISH), respectively. Number and density of both TH immunoreactive and TH cRNA labeled cells were increased in the pars reticulata of the substantia nigra (SNr) 8 h after single administration of a dopamine antagonist haloperidol. At the same time number and density of TH positive cells remained unchanged in a ventro-medial, dorso-medial or lateral part of the pars compacta (SNc) and in the pars lateralis (SNl) of the substantia nigra. A D2 receptor-specific agonist, quinpirole, was without effect on either ISH or IMHC in any of these areas, including the SNr. These results reveal the existence of a population of TH-negative neurons in the SNr, in which TH gene-expression can be activated through a dopamine receptor-mediated mechanism, leading to detectable levels of both TH and TH mRNA. Furthermore they suggest that TH gene-expression in these neurons normally is inhibited by dopamine released from somata and dendrites in the SNr.

Effects of nerve growth factor infusion on behavioral recovery and graft survival following intraventricular adrenal medulla grafts in the unilateral 6-hydroxydopamine lesioned rat

NGF was infused into the lateral ventricle of rats with unilateral 6-OHDA lesions of the substantia nigra along with adrenal medulla or control grafts. Treatment effectiveness, as measured by amphetamine-induced turning behavior, indicated that there were no significant differences between treated and control groups in spite of the survival of tyrosine hydroxylase (TH) immunoreactive grafts. Furthermore, adrenal medulla graft survival was not dependent on NGF infusion. These results indicate that TH-positive graft survival is not correlated with behavioral recovery as assessed by amphetamine-induced turning. These results differ from studies which utilized apomorphine-induced turning as a measure of behavioral recovery. We propose that adrenal medulla graft survival alone is not sufficient to promote behavioral recovery in the 6-OHDA lesioned rat.

(-)deprenyl increases activities of superoxide dismutase and catalase in certain brain regions in old male mice

A subcutaneous continuous infusion of (-)deprenyl for 3 weeks in old C57BL male mice increased superoxide dismutase (SOD) and catalase (CAT) activities in s. nigra, striatum and cerebral cortex but not in hippocampus, cerebellum or liver. The doses of 0.5 and 1.0 mg/kg/day were most effective, while with a higher dose (2.0 mg/kg/day), deprenyl tended to lose its effect slightly and with a lower dose (0.25 mg/kg/day) deprenyl was clearly less effective. The results suggest that deprenyl can increase antioxidant enzyme activities in certain brain regions in mice as was previously demonstrated in rats of both sexes and different ages; this raises the possibility that deprenyl has this particular effect in animal species other than rats.

Chronic cocaine administration increases CNS tyrosine hydroxylase enzyme activity and mRNA levels and tryptophan hydroxylase enzyme activity levels

Cocaine is an inhibitor of dopamine and serotonin reuptake by synaptic terminals and has potent reinforcing effects that lead to its abuse. Tyrosine hydroxylase (TH) and tryptophan hydroxylase (TPH) catalyze the rate-limiting steps in dopamine and serotonin biosynthesis, respectively, and are the subject of dynamic regulatory mechanisms that could be sensitive to the actions of cocaine. This study assessed the effects of chronic cocaine on brain TH and TPH activities. Cocaine was administered (0.33 mg/infusion, i.v.) to rats for 7 days every 8 min for 6 h per day. This administration schedule is similar to patterns of self-administration by rats when given ad libitum access to this dose. This chronic, response-independent administration increased TH enzyme activity in the substantia nigra (30%) and ventral tegmental area (43%). Moreover, TH mRNA levels were also increased (45 and 50%, respectively). In contrast to the enzymatic and molecular biological changes in the cell bodies, TH activity was unchanged in the terminal fields (corpus striatum and nucleus accumbens). Similarly, TPH activity was increased by 50% in the raphe nucleus (serotonergic cell bodies). In summary, the chronic response-independent administration of cocaine produces increases in the expression of TH mRNA and activity in both the cell bodies of motor (nigrostriatal) and reinforcement (mesolimbic) dopamine pathways. These increases are not manifested in the terminal fields of these pathways.

Protective actions of human recombinant basic fibroblast growth factor on MPTP-lesioned nigrostriatal dopamine neurons after intraventricular infusion

Basic fibroblast growth factor (bFGF, FGF-2) is a trophic factor for neurons and astrocytes and has recently been demonstrated in the vast majority of dopamine (DA) neurons of the ventral midbrain of the rat. Potential neuroprotective actions of FGF-2 in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) model have also been reported. The actions of the FGF-2 have now been further analyzed in a combined morphological and behavioural analysis in the MPTP model of the adult black mouse, using a continuous human recombinant FGF-2 (hrFGF-2) intraventricular (i.v.t.) administration in a heparin-containing (10 IU heparin/ml) mock cerebrospinal fluid (CSF) solution. Tyrosine hydroxylase (TH) immunocytochemistry in combination with computer assisted microdensitometry demonstrated a counteraction of the MPTP-induced disappearance of neostriatal TH-immunoreactive (ir) nerve terminals following the FGF-2 treatment. Unbiased estimates of the total number of nigral TH ir neurons, using stereological methods involving the optical disector (Olympus), showed that the MPTP-induced reduction in the number of nigral TH ir nerve cell bodies counterstained with cresyl violet (CV; by 56%) was partially counteracted by the FGF-2 treatment (by 26%). The behavioral analysis demonstrated an almost full recovery of the MPTP-induced reduction of the locomotor activity after FGF-2 treatment. This action was maintained also 1 week after cessation of treatment. The hrFGF-2 produced an astroglial reaction as determined in the lateral neostriatum and in the substantia nigra (SN) far from the site of the infusion, indicating that the growth factor may have reached these regions by diffusion to activate the astroglia. Immunocytochemistry revealed FGF-2 immunoreactivity (IR) in the nuclei of the astroglia cell population in the dorsomedial striatum and the microdensitometric and morphometric evaluation demonstrated an increase in the number, but not in the intensity, of these profiles on the cannulated side, suggesting the possibility that hrFGF-2 stimulates FGF-2 synthesis in astroglial cells with low endogenous FGF-2 IR. These results indicate that hrFGF-2, directly and/or indirectly via astroglia, upon i.v.t. infusion exerts trophic effects on the nigrostriatal DA system and may increase survival of nigrostriatal DA nerve cells exposed to the MPTP neurotoxin

The competitive NMDA antagonist CPP protects substantia nigra neurons from MPTP-induced degeneration in primates

Degeneration of nigrostriatal dopaminergic neurons is the primary histopathological feature of Parkinson's disease. The neurotoxin MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine) induces a neurological syndrome in man and non-human primates very similar to idiopathic Parkinson's disease by selectively destroying dopaminergic nigrostriatal neurons. This gives rise to the hypothesis that Parkinson's disease may be caused by endogenous or environmental toxins. Endogenous excitatory amino acids (EAAs) such as L-glutamate could be involved in neurodegenerative disorders including Parkinson's disease. We report in this study that the competitive NMDA antagonist CPP (3-((+/-)-2-carboxypiperazin-4-yl)-propyl-1-phosphonic acid) protects nigral tyrosine hydroxylase (TH) positive neurons from degeneration induced by systemic treatment with MPTP in common marmosets. This indicates that EAAs are involved in the pathophysiological cascade of MPTP-induced neuronal cell death and that EAA antagonists may offer a neuroprotective therapy for Parkinson's disease.

Noncholinergic functions of cholinesterases

Cholinesterases (acetylcholinesterase and butyrylcholinesterase) exhibit additional catalytic activities apart from their well-known action in hydrolyzing choline esters. An amine-sensitive aryl acylamidase activity is exhibited by both acetyl- and butyrylcholinesterases. A metallocarboxypeptidase-like activity is found associated with both acetyl- and butyrylcholinesterases. The peptidase activity exhibited by butyrylcholinesterase was located in a 50-kDa COOH-terminal fragment. Acetylcholinesterase is implicated in noncholinergic functions in the substantia nigra. A relationship between tumorigenesis, cell differentiation, and cholinesterases has been speculated. The sequence similarities between different esterases, lipases, thyroglobulin, cell adhesion proteins, and cholinesterases would make it appear that cholinesterases are capable of exhibiting more than one biological activity and their functions are wider than what is hitherto known.

Chronic levodopa administration alters cerebral mitochondrial respiratory chain activity

Parkinson's disease (PD) is characterized mainly by a loss of nigrostriatal dopamine neurons. Thus far, the actual physiopathology of PD remains uncertain, although recent studies have found decreased activity of complex I, one of the enzymatic units of the mitochondrial respiratory chain, in various tissues of PD patients. Because most, if not all, of PD patients are treated chronically with levodopa, the precursor of dopamine, and because we have shown previously that catecholamines may alter mitochondrial respiration, we assessed the effects of chronic administration of levodopa on complex I activity in rat brain. We found that chronic administration of levodopa, at a dose used in PD patients, caused a significant reduction in complex I activity while it did not affect the activities of complex II, complex IV, and citrate synthase. Reduction in complex I activity correlated well with catecholamine innervation as the reduction was observed mainly in the striatum and substantia nigra and to a lesser extent in the frontal cortex but not in the cerebellum. Moreover, the levodopa-induced decrease of complex I activity was reversible since activities at 1, 3, and 7 days after the last injection showed a progressive return to control values. Incubation of whole brain mitochondria in vitro showed that both levodopa and dopamine inhibit complex I activity in a dose- and time-dependent manner. In contrast, other compounds such as homovanillic acid, 3,4-dihydroxyphenylacetic acid, and 3-O-methyl-dopa were minimally effective. Reduced glutathione, ascorbate, superoxide dismutase, and catalase prevented the effect of levodopa and dopamine on complex I. Various inhibitors of monoamine oxidase also prevented the effect of dopamine.(ABSTRACT TRUNCATED AT 250 WORDS)

L-694,247: a potent 5-HT1D receptor agonist

1. The 5-hydroxytryptamine (5-HT) receptor binding selectivity profile of a novel, potent 5-HT1D receptor agonist, L-694,247 (2-[5-[3-(4-methylsulphonylamino)benzyl-1,2,4-oxadiazol-5-yl ]- 1H-indole-3-yl]ethylamine) was assessed and compared with that of the 5-HT1-like receptor agonist, sumatriptan. 2. L-694,247 had an affinity (pIC50) of 10.03 at the 5-HT1D binding site and 9.08 at the 5-HT1B binding site (sumatriptan: pIC50 values 8.22 and 5.94 respectively). L-694,247 retained good selectivity with respect to the 5-HT1A binding site (pIC50 = 8.64), the 5-HT1C binding site (6.42), the 5-HT2 binding site (6.50) and the 5-HT1E binding site (5.66). The pIC50 values for sumatriptan at these radioligand binding sites were 6.14, 5.0, < 5.0 and 5.64 respectively. Both L-694,247 and sumatriptan were essentially inactive at the 5-HT3 recognition site. 3. L-694,247, like sumatriptan, displayed a similar efficacy to 5-HT in inhibiting forskolin-stimulated adenylyl cyclase in guinea-pig substantia nigra although L-694,247 (pEC50 = 9.1) was more potent than sumatriptan (6.2) in this 5-HT1D receptor mediated functional response. L-694,247 (pEC50 = 9.4) was also more potent than sumatriptan (6.5) in a second 5-HT1D receptor mediated functional response, the inhibition of K(+)-evoked [3H]-5-HT release from guinea-pig frontal cortex slices. 4. The excellent agreement observed for L-694,247 between the 5-HTlD radioligand binding affinity and the functional potency confirm that the two functional models (the inhibition of forskolin-stimulated adenylyl cyclase in guinea-pig substantia nigra and the inhibition of K+-evoked [3H]-5-HT release from guinea-pig frontal cortex) do indeed reflect 5-HTID-mediated events.5. L-694,247 is a novel, highly potent 5-HTID/5-HTIB receptor ligand which should prove useful for the exploration of the physiological role of these receptors in animals.

Deprenyl increases survival of rat foetal nigral neurones in culture

To study the potential of L-deprenyl to rescue dopaminergic neurones from natural death in primary cultures, foetal nigral neurones were prepared from the ventral midbrain of 16 day old rat embryos. L-deprenyl, at final concentrations of 0.1, 1 and 10 microM, or vehicle solution was added to the culture medium. The cells were allowed to survive for 1, 5 and 10 days. They were then fixed and stained for tyrosine hydroxylase (TH) immunohistochemistry, with or without histological staining. After 5 and 10 days, deprenyl at 0.1 microM increases the number of TH-positive profiles in treated cultures when compared with controls but the effect was more evident at 1 and 10 microM. This can be interpreted as increased survival of catecholaminergic neurones. We cannot however rule out the possibility that deprenyl stimulates the expression of TH by other neurones.

Differential cholinergic and non-cholinergic actions of acetylcholinesterase in the substantia nigra revealed by fasciculin-induced inhibition

The effects of the peptide fasciculin (FAS), a potent inhibitor of acetylcholinesterase (AChE) have been examined, following unilateral microinfusion, on tissue levels of monoamines in the rat substantia nigra and concomitant circling behaviour. Although FAS inhibited 87% of total AChE, the levels of dopamine and its metabolites remained unchanged. Furthermore, the treatment induced modest contraversive rotation which was markedly enhanced in the presence of a systemic challenge with apomorphine. This behavioural effect of FAS was partially reversed by systemically administered atropine. Any possible interaction of FAS with nigral dopamine systems was further investigated by testing the peptide in animals that five days earlier had undergone a 6-hydroxydopamine (6-OHDA) lesion of the SN such that dopamine and AChE were significantly but not completely reduced. In a majority of these animals, FAS treatment caused a reversal of the lesion induced ipsiversive rotation, ie restored contraversive rotation. It is concluded that in the SN, FAS can have biochemical and behavioural actions independent of local dopamine systems and linked to cholinergic transmission. In addition, treatment with FAS in the substantia nigra also reveals the possible existence of at least two distinct pools of AChE with, respectively, non-cholinergic and cholinergic actions.

Preferential expression of superoxide dismutase messenger RNA in melanized neurons in human mesencephalon

The copper-zinc-dependent superoxide dismutase messenger RNA expression was studied at cellular level by in situ hybridization, using a 35S-labelled complementary DNA probe homologous to human copper-zinc-dependent superoxide dismutase messenger RNA, in the dopaminergic neuron-containing areas of the human mesencephalon (the substantia nigra pars compacta, ventral tegmental area, central gray substance and peri- and retrorubral region corresponding to catecholaminergic cell group A8). The autoradiographic labelling signal was localized in neurons. No detectable hybridization signal could be found in the glial cells. Copper-zinc-dependent superoxide dismutase messenger RNA was detected in melanin-containing neurons as well as in non-melanized neurons. Quantification at cellular level, taking the autoradiographic silver grain density as an index of the abundance of copper-zinc-dependent superoxide dismutase messenger RNA, indicated that hybridization level was higher in the melanized than in the non-melanized neurons within a region. Among melanized neurons, cellular copper-zinc-dependent superoxide dismutase messenger RNA content was lowest in the neurons of the substantia nigra. No significant difference in levels of transcripts was evidenced between the groups of non-melanized neurons. The data suggest that the abundance of copper-zinc-dependent superoxide dismutase messenger RNA is higher in the mesencephalic neurons containing neuromelanin compared to other neurons. Thus, the melanized neurons have a particular defence system against oxygen toxicity, which may represent a basis for their preferential vulnerability to Parkinson's disease.

A comparison of solid intraventricular and dissociated intraparenchymal fetal substantia nigra grafts in a rat model of Parkinson's disease: impaired graft survival is associated with high baseline rotational behavior

It has been established that substantia nigra (SN) grafts can produce a behavioral effect in animal models of Parkinson's disease when transplanted either into the lateral ventricles as solid tissue fragments or directly into the striatum as dissociated cells. These two transplantation methods (solid-intraventricular and dissociated-intraparenchymal) were directly compared in the present study. Adult male rats received unilateral SN lesions by stereotaxic injection of 6-hydroxydopamine. Fetal ventral mesencephalon, containing the SN, was harvested from 15-day gestational rat fetuses. Equal weights of tissue were transplanted, either as solid-intraventricular or dissociated-intraparenchymal grafts. In the animals with surviving grafts, similar decreases in apomorphine-induced rotational behavior were seen in both dissociated (40.2% at 6 weeks, 29.6% at 12 weeks, N = 12) and solid (31.8% at 6 weeks, 51.0% at 12 weeks, N = 11) graft groups. Control animals receiving tectal grafts showed smaller decreases (dissociated: 12.6% at 6 weeks, 18.8% at 12 weeks, N = 20; solid: 4.1% at 6 weeks, 8.0% at 12 weeks, N = 20). There were no significant overall differences between the effects of the solid and dissociated grafts; however, in the subgroup of animals with high baseline levels of rotational behavior, the solid-intraventricular grafts produced a significantly larger effect then did the dissociated-intraparenchymal SN grafts. There was also a tendency for the effect of the solid-intraventricular grafts to increase gradually over the 12-week testing period, whereas the effects of the dissociated-intraparenchymal grafts were maximal by 6 weeks after transplantation. For both SN graft groups, there were significant correlations between decreases in rotation and numbers of surviving tyrosine hydroxylase-immunoreactive neurons in the grafts. It was also found that animals with no surviving transplanted tyrosine hydroxylase-positive neurons had higher baseline levels of rotational behavior. Therefore, in the present model, solid-intraventricular and dissociated-intraparenchymal SN grafts have similar effects on apomorphine-induced rotational behavior, except that the solid-intraventricular grafts tended to produce a larger effect in animals with high baseline levels of rotational behavior.

Codistribution of choleratoxin binding sites and tyrosine hydroxylase/FGF-2 immunoreactive nigral nerve cells

By means of light and confocal laser microscopical analysis of choleratoxin (CT) binding sites indicating the localization of the ganglioside GM1, evidence has been obtained for the presence of ganglioside GM1 in discrete nerve terminals, some of them identified by synapsin-1 immunoreactivity (IR), with a focal distribution in the nerve terminal membrane. Double immunolabelling studies demonstrate that GM1 positive nerve terminals are associated with tyrosine hydroxylase/fibroblast growth factor-2 (TH/FGF-2) immunoreactive dopamine (DA) perikarya in the zona compacta of the rat substantia nigra. It is suggested that GM1 may be released from these terminals to become incorporated into the nerve cell membrane of the FGF-2-containing DA nigral nerve cells, where they may enhance the activity of neurotrophic factor receptors such as those for FGF-2.

Intracellular distribution of monoamine oxidase A in selected regions of rat and monkey brain and spinal cord

Monoamine oxidase A and B (MAO A and B; EC 1.4.3.4) are integral proteins of the outer mitochondrial membrane that degrade monoamines including the neurotransmitters norepinephrine, dopamine, and serotonin. In this study, monoclonal antibodies that recognize rat or monkey MAO A were used in immunocytochemical studies to visualize the subcellular localization of this enzyme within neurons in the central nervous system of these species. The regions examined included the locus coeruleus, substantia nigra, spinal cord, and pallidostriatum, which are known to contain MAO A-positive structures. Ultrastructural studies revealed that most MAO A staining was associated with the outer membrane of mitochondria, within the cell bodies, dendrites, axons and terminals. However, some immunoreactive staining for MAO A was also observed in the rough endoplasmic reticulum in the cell bodies. Staining for mitochondrial MAO A in dendrites was observed in terminal fields of the monoamine system, including the spinal cord and the pallidostriatum. The intensity of staining also increased in the subsynaptic density. MAO A was also found associated with mitochondria in ependymal cells lining the fourth ventricle adjacent to the locus coeruleus and in the endothelial cells lining the blood vessels. Localization of MAO A in noradrenergic neurons, ependymal cells, and subsynaptic regions of dendrites in monoamine terminal fields supports the concept that this neurotransmitter-degrading enzyme may play a protective role in the central nervous system.

Regional specificity of the long-term regulation of tyrosine hydroxylase in some catecholaminergic rat brainstem areas. I. Influence of long-term hypoxia

The present study was carried out to investigate the influence of long-term hypoxia on tyrosine hydroxylase (TH) protein quantity in some catecholaminergic rat brainstem areas such as the dorsomedial medulla (DMM), the ventrolateral medulla (VLM) and the locus coeruleus (LC). TH protein quantity was also measured in a dopaminergic structure, the substantia nigra (SN). Male Sprague-Dawley rats were exposed to normobaric hypoxia (10% O2/90% N2) for 3, 7, 14 or 22 days. Controls were kept in normoxia for the same period. This study demonstrates that: (1) 3 days of hypoxia produced a 50% and a 26% increase in the quantity of TH protein in the rostral and caudal LC, respectively; (2) 14 days of hypoxia produced a 44% increase of TH protein content exclusively in the caudal part of DMM and a 31% increase in the VLM area; and (3) the stimulus failed to alter the TH protein quantity in the SN. After 14 and 22 days of hypoxia respectively, the TH protein content in the LC and DMM returned to the level of controls. To determine whether the increase in TH protein quantity could be related to a change in norepinephrine (NE) content, the rate constant of disappearance (k) of NE was measured in the catecholaminergic areas of intact or chemodenervated rats submitted to long-term hypoxia. Our results show that hypoxia causes an increase of TH protein quantity within the subpopulations of catecholaminergic areas additionally with an elevation in the NE content. These data suggest a selective response of the TH regulation to long-term hypoxia within the caudal DMM catecholaminergic area which receives chemosensory inputs.

No evidence for altered muscle mitochondrial function in Parkinson's disease

Recent reports indicate that reductions in mitochondrial respiratory chain function occur in substantia nigra, platelets, and muscle from patients with Parkinson's disease. To confirm and further characterise the presence of a generally distributed mitochondrial defect, mitochondrial metabolism was evaluated in muscle obtained from subjects with Parkinson's disease and from normal controls. Oxygen consumption rates in muscle mitochondria represented by complex I, complexes II-III, or complex IV did not differ between the two groups. Likewise, activities of rotenone sensitive NADH cytochrome c reductase, succinate cytochrome c reductase, or cytochrome oxidase in muscle mitochondria were not significantly different between Parkinsonian and control subjects. These findings fail to provide support for a generalised defect in mitochondrial function in Parkinson's disease but do not exclude an abnormality in respiratory function confined to the substantia nigra.

Four isoforms of tyrosine hydroxylase are expressed in human brain

In contrast to nonprimate species, the RNA for human tyrosine hydroxylase, the rate-limiting enzyme in catecholamine biosynthesis, can undergo alternative splicing to produce four different types of mRNA. Although types 1 and 2 of these human tyrosine hydroxylase mRNAs have been identified in human brain, whether types 3 and 4 human tyrosine hydroxylase mRNAs are present in the central nervous system remains controversial. Furthermore, little is known about the expression of the protein products of these mRNAs in human brain. In this study we used antibodies raised against different octapeptide sequences from each of the predicted human tyrosine hydroxylase protein forms to determine the presence and distribution of each human tyrosine hydroxylase isoforms in several regions of human brain. Control immunocytochemical and blot immunolabeling experiments demonstrated that each antibody selectively recognized the human tyrosine hydroxylase isoform against which it was directed. In immunocytochemical studies, all four human tyrosine hydroxylase isoforms were clearly detectable in neurons of both the substantia nigra and locus coeruleus. The presence of all four isoforms in these nuclei was confirmed with blot immunolabeling studies. Single-label immunocytochemical studies of adjacent sections as well as dual-label comparisons of immunoreactivity for human tyrosine hydroxylase type 1 with type 2, type 3, or type 4 suggested that at least some neurons in these brain regions contain all four human tyrosine hydroxylase isoforms. In contrast, some neurons of the mesencephalon appeared to be selectively immunoreactive with the antibodies against type 1. In the caudate nucleus and putamen, the terminal zones of the dopaminergic projection from the substantia nigra, all four isoforms were detected, although in immunocytochemical studies type 1 appeared to be the predominant isoform present in axons and terminals. These findings demonstrate that human brain contains four distinct isoforms of human tyrosine hydroxylase and that the presence or relative amount of each isoform may differ among catecholaminergic cell populations and between catecholaminergic neurons and terminal fields. These patterns of expression may have important implications for understanding the regulation of catecholamine biosynthesis in human brain both in normal and pathological states.

An immunoelectron microscopic study of pig substantia nigra shows co-localization of endopeptidase-24.11 with substance P

Endopeptidase-24.11 is a widely distributed cell surface enzyme with a role in inactivating some neuropeptides and peptide hormones. In the central nervous system it has been implicated in the metabolism of enkephalins and tachykinins, neuropeptides which are expressed by neurons projecting to the substantia nigra. Two immunochemical methods have been used to reveal the ultrastructural localization of endopeptidase-24.11 and substance P in the substantia nigra of piglets. In the first approach, substance P was revealed by immunoperoxidase staining using the rat monoclonal antibody, NC1, and endopeptidase-24.11 by 1 nm colloidal gold using an affinity-purified rabbit polyclonal antibody, both being applied at the pre-embedding stage. NC1 was shown to be highly specific for substance P, with negligible cross-reactivity with neurokinins A and B. The specificity of the immunostaining was confirmed by processing all sections for both markers, even when only one primary antibody was applied. In the second approach, ultrathin cryosections were immunostained using gold particles of different diameters. In a survey of electron micrographs, 80% of the silver-enhanced gold particles were touching neuronal membranes, consistent with the known topology of endopeptidase-24.11. Endopeptidase-24.11 immunoreactivity was observed both on membranes of axons and on pre- and postsynaptic elements. Substance P immunoreactivity was seen within some boutons, apparently associated with vesicles, and in axons. In doubly stained sections, many examples of immunopositive gold-labelled boutons (i.e. endopeptidase-24.11-immunoreactive-positive) containing immunoperoxidase reaction product (i.e. substance P-immunoreactive-positive) were recorded. In ultrathin cryosections, substance P immunoreactivity was mainly observed in dense-core vesicles within boutons, some of which also showed membrane-associated gold particles marking endopeptidase-24.11 immunoreactivity. This is the first demonstration of endopeptidase-24.11 by immunogold at the electron microscopic level and the first demonstration of the ultrastructural co-localization of a membrane peptidase and its putative neuropeptide target. The results lend strong support to the view that endopeptidase-24.11 has a physiological role in the metabolism of substance P, but do not exclude a role in the inactivation of other neuropeptides.

Chronic intranigral administration of brain-derived neurotrophic factor produces striatal dopaminergic hypofunction in unlesioned adult rats and fails to attenuate the decline of striatal dopaminergic function following medial forebrain bundle transection

The present study determined the effects of chronic intranigral injections of recombinant human brain-derived neurotrophic factor (1 micrograms) every second day for 19 days on the functional capacity of dopaminergic neurons of the nigrostriatal pathway of unlesioned adult rats. In animals chronically treated with brain-derived neurotrophic factor, we observed amphetamine (5 mg/kg)-induced circling behavior directed toward the neurotrophin-injected side (33 turns/5 min). The behavioral asymmetry was paralleled by reductions of striatal [3H]dopamine uptake (27%), tyrosine hydroxylase activity (68%), dopamine content (36%) and [3H]mazindol binding site density (35%) on the same side as brain-derived neurotrophic factor treatment. While chronic injections of brain-derived neurotrophic factor produced a modest decrease in the number of tyrosine hydroxylase-positive cell bodies in the vicinity of the injection site, a similar reduction in cell number was observed in animals injected with a control protein, cytochrome c. However, in contrast to the animals treated with brain-derived neurotrophic factor, rats treated with the control protein showed no amphetamine-induced circling behavior, and there were no significant reductions in neurochemical parameters of striatal dopaminergic function. Lastly, we found that in brain-derived neutrophic factor-injected animals there was a 30% decrease of tyrosine hydroxylase messenger RNA levels in the ventral mesencephalon. We also determined the effects of brain-derived neurotrophic factor treatment on animals with transections of the medial forebrain bundle. Medial forebrain bundle-lesioned animals challenged with amphetamine circled (55 turns/5 min) ipsilateral to the lesioned side. The medial forebrain lesions decreased the following markers of striatal dopaminergic function: [3H]opamine uptake (65%), tyrosine hydroxylase activity (79%), dopamine content (80%) and [3H]mazindol binding site density (52%), induced a pronounced loss of tyrosine hydroxylase-positive cell bodies within the substantia nigra and also reduced tyrosine hydroxylase messenger RNA levels. Chronic intranigral brain-derived neurotrophic factor treatment did not attenuate nor did it exacerbate the medial forebrain bundle lesion-induced decreases of dopaminergic parameters in either the substantia nigra or striatum. The results of the present study indicate that chronic intranigral administration of brain-derived neurotrophic factor to normal adult rats induces a dopaminergic hypofunction in the striatum which is manifested behaviorally by amphetamine-induced rotations. The brain-derived neurotrophic factor-induced striatal function is not the result of significant cell loss at the levels of the substantia nigra, but seems to be related to brain-derived neurotrophic factor-induced down-regulation of dopaminergic-specific proteins.(ABSTRACT TRUNCATED AT 400 WORDS)

Direct in vivo gene transfer to ependymal cells in the central nervous system using recombinant adenovirus vectors

To evaluate the potential for adenovirus-mediated central nervous system (CNS) gene transfer, the replication deficient recombinant adenovirus vectors Ad.RSV beta gal (coding for beta-galactosidase) and Ad-alpha 1AT (coding for human alpha 1-antitrypsin) were administered to the lateral ventricle of rats. Ad.RSV beta gal transferred beta-galactosidase to ependymal cells lining the ventricles whereas Ad-alpha 1AT mediated alpha 1-antitrypsin secretion into the cerebral spinal fluid for 1 week. These observations, together with beta-galactosidase activity in the globus pallidus and substantia nigra following stereotactic administration of Ad.RSV beta gal to the globus pallidus, suggest that adenovirus vectors will be useful for CNS gene therapy.

Convergent regulation by ciliary neurotrophic factor and dopamine of tyrosine hydroxylase expression in cultures of rat substantia nigra

Ciliary neurotrophic factor and dopamine were found to enhance the expression of tyrosine hydroxylase immunoreactivity in cultured neurons from the substantia nigra of 16-day-old rat fetuses. The number of tyrosine hydroxylase-positive cells decreased progressively to approximately 30% by 96 h. Treatment with 5 microM dopamine maintained the tyrosine hydroxylase-positive neurons at 60% for 48 h, but not for longer. Concurrent treatment with 5 microM dopamine and 20 trophic units/ml ciliary neurotrophic factor had a greater impact on tyrosine hydroxylase-positive cells, resulting in the maintenance of 70% of the initial number for up to 72 h, but not beyond that time. When dopamine or dopamine/ciliary neurotrophic factor treatments were applied for 24 h after a 48-h delay, the number of tyrosine hydroxylase-positive cells was restored to 60 and 80%, respectively, but not restoration was observed with 96-h delayed treatments. These results suggest that dopamine and ciliary neurotrophic factor, alone or in combination, are not able to support the survival of tyrosine hydroxylase-positive neurons, but reduce their apparent numerical loss by enhancing the expression of tyrosine hydroxylase. The effects of dopamine, alone or in combination with ciliary neurotrophic factor, were predominantly mediated by D2 receptors, since they were blocked by selective D2 receptor antagonists and since the D2 receptor agonist quinpirole was able to substitute for dopamine. The effects of dopamine and ciliary neurotrophic factor were similar in astroblast-rich and in astroblast-depleted cultures, suggesting that they were not mediated through glial cells. These results extend our previous observations on locus coeruleus cultures, in which the concurrent treatment with ciliary neurotrophic factor and norepinephrine was shown to enhance tyrosine hydroxylase expression (but not survival) of noradrenergic neurons. They also consolidate the view that ciliary neurotrophic factor and the neuron's own transmitter act in convergence and in an autocrine/paracrine mode as regulators of the corresponding neurotransmitter phenotype.