Influence of age and time interval between death and autopsy on dopamine and 3-methoxytyramine levels in human basal ganglia

The caudate nuclei and putamens of 30 human brains were analyzed for dopamine and its metabolite 3-methoxytyramine, most of which was presumably formed from dopamine postmortally. It was found that dopamine and the sum (dopamine + methoxytyramine) but not methoxytyramine declined with the time interval between death and autopsy as well as with age.

NMDA receptor losses in putamen from patients with Huntington's disease

N-Methyl-D-aspartate (NMDA), phencyclidine (PCP), and quisqualate receptor binding were compared to benzodiazepine, gamma-aminobutyric acid (GABA), and muscarinic cholinergic receptor binding in the putamen and cerebral cortex of individuals with Huntington's disease (HD). NMDA receptor binding was reduced by 93 percent in putamen from HD brains compared to binding in normal brains. Quisqualate and PCP receptor binding were reduced by 67 percent, and the binding to other receptors was reduced by 55 percent or less. Binding to these receptors in the cerebral cortex was unchanged in HD brains. The results support the hypothesis that NMDA receptor-mediated neurotoxicity plays a role in the pathophysiology of Huntington's disease.

Bimodal distribution of dopamine receptor densities in brains of schizophrenics

The dopamine hypothesis of schizophrenia was examined by measuring the density of dopamine receptors in the postmortem brains of 81 control subjects and 59 schizophrenics from four different countries. The densities of dopamine receptors in the tissues from the schizophrenic patients had a bimodal distribution in the caudate nucleus, putamen, and nucleus accumbens. One mode occurred 25 percent above the control density, and a second mode occurred at a density 2.3 times that of the control density for all three regions. Although almost all the patients had been medicated with neuroleptics, the two modes had the same dissociation constant for the labeled ligand used, suggesting that the neuroleptic doses were similar for the two populations of schizophrenics. The results thus provide direct evidence for two distinct categories of schizophrenia.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine-induced parkinsonism in the common marmoset

The administration of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) (1-4 mg/kg i.p.) for 4 days induced dose-dependent parkinsonism in the common marmoset within 48 h. MPTP produced profound akinesia, rigidity of the trunk and limbs, postural abnormalities, loss of vocalization and, in some cases, postural tremor. In a single animal the administration of L-DOPA in conjunction with a peripheral decarboxylase inhibitor, reversed the parkinsonian symptoms. Subsequent biochemical analysis showed a profound loss of dopamine and [3H]dopamine uptake in the caudate-putamen, but no change in specific [3H]spiperone binding.

Kynurenine pathway measurements in Huntington's disease striatum: evidence for reduced formation of kynurenic acid

Recent evidence suggests that there may be overactivation of the N-methyl-D-aspartate (NMDA) subtype of excitatory amino acid receptors in Huntington's disease (HD). Tryptophan metabolism by the kynurenine pathway produces both quinolinic acid, an NMDA receptor agonist, and kynurenic acid, an NMDA receptor antagonist. In the present study, multiple components of the tyrosine and tryptophan metabolic pathways were quantified in postmortem putamen of 35 control and 30 HD patients, using HPLC with 16-sensor electrochemical detection. Consistent with previous reports in HD putamen, there were significant increases in 5-hydroxyindoleacetic acid, 5-hydroxytryptophan, and serotonin concentrations. Within the kynurenine pathway, the ratio of kynurenine to kynurenic acid was significantly (p less than 0.01) increased twofold in HD patients as compared with controls, consistent with reduced formation of kynurenic acid in HD. CSF concentrations of kynurenic acid were significantly reduced in HD patients as compared with controls and patients with other neurologic diseases. Because kynurenic acid is an endogenous inhibitor of excitatory neurotransmission and can block excitotoxic degeneration in vivo, a relative deficiency of this compound could directly contribute to neuronal degeneration in HD.

Highly sensitive assay for tyrosine hydroxylase activity by high-performance liquid chromatography

A highly sensitive assay for tyrosine hydroxylase (TH) activity by high-performance liquid chromatography (HPLC) with amperometric detection was devised based on the rapid isolation of enzymatically formed DOPA by a double-column procedure, the columns fitted together sequentially (the top column of Amberlite CG-50 and the bottom column of aluminium oxide). DOPA was adsorbed on the second aluminium oxide column, then eluted with 0.5 M hydrochloric acid, and assayed by HPLC with amperometric detection. D-Tyrosine was used for the control. alpha-Methyldopa was added to the incubation mixture as an internal standard after incubation. This assay was more sensitive than radioassays and 5 pmol of DOPA formed enzymatically could be measured in the presence of saturating concentrations of tyrosine and 6-methyltetrahydropterin. The TH activity in 2 mg of human putamen could be easily measured, and this method was found to be particularly suitable for the assay of TH activity in a small number of nuclei from animal and human brain.

Ascending catecholamine pathways and amphetamine-induced locomotor activity: importance of dopamine and apparent non-involvement of norepinephrine

Stereotaxically placed intracerebral microinjections of 6-hydroxydopamine (6-OHDA) were used to produce selective and extensive lesions of either the dopaminergic nigro-neostriatal bundle or the dorsal and ventral noradrenergic projections in the rat. The extensive damage of the noradrenergic pathways which is typically obtained after intranigral 6-OHDA injections was completely prevented by pretreatment with desipramine. Extensive depletions (85-95%) of norepinephrine (NE) in the hypothalamus, cerebral cortices and hippocampi failed to influence either spontaneous or D-amphetamine-induced locomotor activity. Neither the time course of the amphetamine response as measured by photocell cages nor the qualitative nature of the response as determined by direct observation was significantly altered by these lesions. In contrast, selective depletion (92%) of neostriatal dopamine (DA) after intranigral 6-OHDA injections severly reduced but did not abolish amphetamine-induced hyperkinesia. At the highest dose studied (2.0 mg/kg) these animals showed an initial increase in activity but, unlike controls, failed to maintain this level. This response was probably mediated by the small remaining stores of DA in the neostriatum. Pimozide (0.5 mg/kg) also severely attenuated but did not abolish amphetamine-induced locomotor activity. These data are consistent with the view that ascending DA projections are a critical substrate for amphetamine-induced hyperkinesia. They furthermore suggest that ascending NE systems do not play a role in this response.

Immunocytochemical localization of calmodulin and a heat-labile calmodulin-binding protein (CaM-BP80) in basal ganglia of mouse brain

Antisera to calmodulin, a Ca2%-dependent modulator protein, and a heat-labile calmodulin-binding protein have been used to localize these proteins in mouse caudate-putamen. The two proteins appear to be located at identical sites in this brain area. At the light microscopic level, calmodulin and calmodulin-binding protein are found within the cytoplasm and processes of large cells. At the electron microscopic level the proteins are associated with neuronal elements only, primarily at postsynaptic sites within neuronal somata and dendrites. Within the dendrites the immunocytochemical label is associated predominantly with the postsynaptic density and dendritic microtubules. These results are in accord with recent biochemical and immunihistochemical studies of calmodulin in brain and in dividing cells. Thus, calmodulin and the heat-labile calmodulin-binding protein may play a role in the nervous system at the site of neurotransmitter action and at the level of microtubular function.

Survival of basal ganglia neuropeptide Y-somatostatin neurones in Huntington's disease

The content of somatostatin-like immunoreactivity (SRIF-LI) and neuropeptide Y-like immunoreactivity (NPY-LI) has been measured in both control post-mortem human brains and in Huntington's disease brains. The content of both SRIF-LI and NPY-LI was found to be significantly increased in the basal ganglia of Huntington's disease brains compared with a control group. The nature of the SRIF-LI and NPY-LI in both control and Huntington's disease brains was investigated after separation on Sephadex G25 and G50 columns. Using a C-terminal-directed SRIF radioimmunoassay (RIA), 3 peaks of immunoreactivity were measured, whilst an N-terminal-directed SRIF RIA detected two peaks of immunoreactivity. In each case, the elution profile did not differ between control and Huntington's disease caudate nucleus. The content of immunoreactivity in each peak was found to be increased in Huntington's disease brains compared with controls. Only one peak of NPY-LI was detected in both control and Huntington's disease caudate after separation on Sephadex G25 and G50 columns. Immunohistochemical staining of the caudate and putamen of control and Huntington's disease brains revealed a population of neurones containing NPY-LI. The number of NPY-positive neurones was found to be increased in both the caudate and putamen of Huntington's disease brains compared to control caudate and putamen.

Parkinson plus syndrome: diagnosis using high field MR imaging of brain iron

The distribution of iron in the brain was analyzed using high field strength (1.5 T) magnetic resonance (MR) imaging in 14 healthy control individuals and six patients with Parkinson plus syndromes (multisystem atrophy and progressive supranuclear palsy) who were unresponsive to antiparkinsonian therapy. The normal topographic distribution of iron in the brain as indicated by high field MR images coincided precisely with the distribution of iron in the brain as determined by Perls staining for ferric iron. In Parkinson plus syndromes, there were abnormally increased concentrations of iron (decreased T2 relaxation times) in the putamen, and less prominent increases in the caudate nucleus and lateral pars compacta of the substantia nigra. In high field strength MR images of normal patients, the decreased signal intensity in the globus pallidus is more prominent than that of the putamen. In MR images of patients with Parkinson plus syndromes, the decreased signal intensity of the putamen is more prominent than that of the globus pallidus.

Somatostatin is increased in the basal ganglia in Huntington disease

Huntington disease (HD) is an autosomal dominant hereditary disorder characterized by premature cell death, predominantly in the neostriatum. Decreased concentrations of several neurotransmitters and neuropeptides have been reported in the basal ganglia in Huntington disease. We now report that concentrations of radioimmunoassayable somatostatin are increased in extracts of the caudate (mean +/- standard error of the mean, ng/gm net weight; 247 +/- 24 versus 85 +/- 11), putamen (275 +/- 48 versus 74 +/- 11), external globus pallidus (100 +/- 10 versus 27 +/- 6), and internal globus pallidus (108 +/- 21 versus 21 +/- 8) in the disease. The concentrations of immunoreactive substance P measured in the same extracts were markedly reduced in caudate (mean +/- standard error of the mean, pmol/gm wet weight; 25 +/- 3 versus 109 +/- 20), putamen (28 +/- 7 versus 88 +/- 28), external globus pallidus (39 +/- 9 versus 196 +/- 62), and internal globus pallidus (60 +/- 17 versus 263 +/- 39), as well as in both subdivisions of the substantia nigra. Gel permeation chromatography and high-performance liquid chromatography showed radioimmunoassayable somatostatin to include peptides with physicochemical properties of the tetradecapeptide somatostatin and larger substances, including somatostatin-28-like material. A single peak of immunoreactive substance P corresponding to synthetic substance P was found by high performance liquid chromatography. These results suggest that immunoassayable somatostatin-containing neuronal elements in the neostriatum and globus pallidus in Huntington disease are affected differentially by the disease process from neurons that contain immunoreactive substance P.

Age-correlated loss of dopaminergic binding sites in human basal ganglia

Human caudate nucleus, putamen, substantia nigra, and nucleus accumbens were analyzed for the effects of age on dopaminergic binding sites. Decreases in the number of dopaminergic binding sites were detected with age in caudate nucleus (44 specimens from three sample groups) and substantia nigra (n = 12). In caudate nucleus, the decline in [3H]2-amino-6, 7-dehydroxy-1, 2, 3, 4-tetrahydronaphthalene sites was three times greater than for [3H]spiperone, but age changes were significant in only two of the three sampling groups. No age changes in binding were detected in the putamen (n = 44) or nucleus accumbens. Age, sex, and tissue source all significantly contributed to variance. However, cause of death, time from death to tissue freezing, and length of storage did not influence dopaminergic binding in the caudate nucleus or putamen. Relative to the life-span, the age-correlated decrease in dopaminergic binding sites of human brain approximates that in aging rodent striatum. Comparisons of altered dopaminergic binding with other age-correlated changes suggest that neuronal loss may not be involved in the loss of binding sites before midlife.

Quantitative autoradiography of dopamine D2 sites in rat caudate-putamen: localization to intrinsic neurons and not to neocortical afferents

Dopamine D2 receptors, labeled with [3H]spiroperidol or [3H]sulpiride, show a lateral-to-medial gradient in the caudate-putamen, with a more than two-fold greater density laterally than medially. It has been thought that D2 receptors are located on at least two neuronal elements of the caudate-putamen, neurons intrinsic to this structure and axons whose cell bodies reside in the cortex. As a first step in establishing what neuronal elements underlie this heterogeneous organization of D2 receptors, we took advantage of quantitative autoradiography to examine the association of these receptors with those elements. The present findings show that the D2 sites are almost exclusively located on neurons whose somata reside in the caudate-putamen and are not located on terminals of corticostriatal axons. A detailed comparison of the distribution of histochemically identified acetylcholinesterase neurons with that of D2 receptors in serially adjoining sections suggests a common organizational pattern. The density of [3H]spiroperidol sites in rat caudate-putamen was determined after unilateral injection of the neurotoxin quinolinic acid into this structure or after ablation of neocortical regions. Quantification of the tissue damage was achieved by acetylcholinesterase histochemistry (following diisopropylfluorophosphate treatment), as well as by thionin and luxol fast staining of sections adjacent to those used for [3H]spiroperidol autoradiography. In identically treated animals, biochemical determination of the extent of tissue damage was made utilizing assays for high-affinity [3H]choline and [3H]glutamate uptake in the caudate-putamen. In quinolinic acid-injected rats, the density of D2 sites was decreased by 90-95% at the site of complete loss of large acetylcholinesterase-positive neurons. Other animals, given ablations of specific neocortical fields (medial prefrontal, motor, somatosensory) or of the entire parietal-frontal cortex of one hemisphere, showed no loss of caudate-putamen D2 sites unless the cortical ablation caused accompanying damage of the caudate-putamen. In the caudate-putamen of all animals there was a close correspondence between the D2 sites and the striatal neurons (and processes) that show strong acetylcholinesterase reactivity. We suggest that the caudate-putamen topography of D2 sites is based largely on the internal organization of this structure and may preferentially involve acetylcholine-containing intrinsic neurons.

The topographical distribution of serotoninergic terminals in the neostriatum of the rat and the caudate nucleus of the cat

The topographical distribution of serotoninergic terminals in the neostriatum of the rat and the caudate nucleus of the cat was established owing to the combined use of microdissection techniques and biochemical microassays. The density of 5-HT terminals in various areas of both structures was quantified first by measuring 5-HT levels in microdiscs of frozen tissue. Since the high affinity uptake process for 5-HT appeared undamaged in isotonic homogenates of previously frozen (--5 degrees C) tissues, it was possible to confirm the findings obtained with the measurement of 5-HT levels by also determining 5-HT uptake activity in these microdiscs. However, in the rat neostriatum, but not in the cat caudate nucleus, [3H]5-HT even at a very low extracellular concentration (4.4 -x 10(-8) M) was taken up not only by serotoninergic terminals but also to a significant extent by dopaminergic terminals. In presence of benztropine, this second component was suppressed and [3H]5-HT uptake activity could then be considered as a specific marker of serotoninergic terminals also in the neostriatum of the rat. In both species, 5-HT terminals were mainly localized in the ventrocaudal area of the structure. In this area, 5-HT levels were among the highest values found in the brain (17 ng/mg protein). The density of 5-HT terminals decreased progressively from the acudal to the rostral planes of the neostriatum in rats or the caudate nucleus in cats. The poorest area, i.e. the dorsorostral zone, contained about 4 times less 5-HT than the ventrocaudal zone of the structure. Electrolytic lesion of the dorsalis (B7) and centralis superior (B8) raphe nuclei during early life resulted in a large decrease of 5-HT levels (--90%) in various parts of the neostriatum of adult rats. The present findings might be of interest to further analyze the role of serotoninergic neurons in extrapyramidal functions.

External imaging of cerebral muscarinic acetylcholine receptors

A radioiodinated ligand that binds to muscarinic acetylcholine receptors was shown to distribute in the brain by a receptor-mediated process. With single-photon-emission imaging techniques, radioactivity was detected in the cerebrum but not in the cerebellum, whereas with a flow-limited radiotracer, radioactivity was detected in cerebrum and cerebellum. Single-photon-emission computed tomography showed good definition of the caudate putamen and cortex in man.

Detection of 5-S-cysteinyldopamine in human brain

5-S-Cysteinyldopamine was synthesized and used as reference compound in HPLC analyses of extracts from various regions of human brain. The compound could be detected in brain regions rich in dopamine (caudate nucleus, putamen, globus pallidus and substantia nigra) but not in other regions (cerebellum, occipital cortex). The occurrence of 5-S-cysteinyldopamine in dopaminergic brain regions supports the hypothesis that dopamine in part undergoes autoxidation, leading to formation of highly reactive quinones. The newly discovered metabolite may prove useful in future studies of dopamine autoxidation and the possibly resultant cytotoxicity in aging and degenerative brain disorders.

Polyamine changes in reversible cerebral ischemia

Putrescine, spermidine, and spermine levels were measured in the cortex, caudoputamen, and hippocampus of rats during 30 min of severe forebrain ischemia (induced by occlusion of both carotid and vertebral arteries) and subsequent recirculation. During ischemia, polyamine levels did not change significantly. During postischemic recirculation, however, putrescine levels dramatically increased whereas those of spermine and spermidine did not change, with the exception of the severely damaged caudoputamen, where the concentration declined after 24 h. The increase of putrescine is explained by postischemic activation of ornithine decarboxylase and inhibition of S-adenosylmethionine decarboxylase. It is suggested that the accumulation of putrescine during postischemic recirculation may be responsible for the delayed neuronal death occurring after ischemia.

Distribution of DARPP-32 in the basal ganglia: an electron microscopic study

DARPP-32, a dopamine and cyclic AMP-regulated phosphoprotein, has been studied by light and electron microscopical immunocytochemistry in the rat caudatoputamen, globus pallidus and substantia nigra. In the caudatoputamen, DARPP-32 was present in neurons of the medium-sized spiny type. Immunoreactivity for DARPP-32 was present in dendritic spines, dendrites, perikaryal cytoplasm, most but not all nuclei, axons and a small number of axon terminals. Immunoreactive axon terminals in the caudatoputamen formed symmetrical synapses with immunolabeled dendritic shafts or somata. Neurons having indented nuclei were never immunoreactive. In the globus pallidus and substantia nigra pars reticulata, DARPP-32 was present in myelinated and unmyelinated axons and in axon terminals. The labelled axon terminals in these regions formed symmetrical synaptic contacts on unlabelled dendritic shafts or on unlabelled somata. These data suggest that DARPP-32 is present in striatal neurons of the medium-sized spiny type and that these DARPP-32-immunoreactive neurons form symmetrical synapses on target neurons in the globus pallidus and substantia nigra. The presence of DARPP-32 in these striatal neurons and in their axon terminals suggests that DARPP-32 mediates part of the response of medium-size spiny neurons in the striatum to dopamine D-1 receptor activation.

Haloperidol increases proenkephalin mRNA levels in the caudate-putamen of the rat: a quantitative study at the cellular level using in situ hybridization

Previous immunocytochemical studies have shown that the opioid peptides, Met-enkephalin and Leu-enkephalin, are present in medium-sized, spiny projection neurons of the caudate-putamen. It has also been demonstrated that chronic treatment of rats with the dopamine receptor blocker, haloperidol, results in an increase in the levels of enkephalin peptides and proenkephalin mRNA in this brain region. To determine whether this increase in proenkephalin mRNA content is exhibited by all enkephalinergic neurons of the caudate-putamen or by only a subpopulation, we have used in situ nucleic acid hybridization to examine the haloperidol-induced increase in proenkephalin mRNA levels at the cellular level. Results of in situ hybridization suggest that all enkephalinergic neurons in the caudate-putamen can respond to haloperidol treatment with an increase in steady state levels of proenkephalin mRNA, and that the mean induction is an approximate 3-fold increase in the message levels. This suggests that dopamine exerts a tonic inhibitory effect on the expression of the proenkephalin gene in all of the enkephalinergic neurons of the caudate-putamen. Dot blot analysis indicated a 2.4-fold increase in the tissue levels of this mRNA. The agreement between the in situ hybridization results and dot blot analysis supports in situ hybridization as a reliable method for quantitative studies of alterations in neuropeptide precursor mRNAs in the brain.

Dopamine receptors in human and calf brains, using [3H]apomorphine and an antipsychotic drug

In order to develop a better dopamine receptor radioligand, [3H[apomorphine was prepared and tested for dopamine-like binding properties in both calf and human brain tissues. Specific binding of [3H]apomorphine was defined as that binding which occurred in the presence of 1 muM (-)-butaclamol (an inactive neuroleptic) minus that occurring in the presence of 1 muM (+)-butaclamol (active neuroleptic). The specific binding was saturable, the number of sites being double that of specific [3H]dopamine binding, and occurred primarily in dopamine-rich regions of postmortem human brains. The binding had a dissociation constant of 0.9 nM for human caudate (2 nM for calf caudate) and was blocked by dopamine and norepinephrine, but not by isoproterenol or (-)-propranolol, distinguishing it from a beta-adrenergic receptor. Since there was little desorption of [3H]apomorphine, the ligand permits extensive washing during routine assays for dopamine receptors, and facilitates biochemical purification of the receptor.

Dopamine D2 receptor density remains constant in treated Parkinson's disease

D2 dopamine receptor densities were measured in postmortem samples of the caudate nucleus and putamen from 36 parkinsonian patients. The relationship between the age of the patient, duration of the disease, and duration of L-dopa therapy versus density of brain D2 dopamine receptors was examined using [3H]spiperone. Receptor density in parkinsonian tissues was constant over the age range of 56 to 90 years, as was the case for control tissues. Density did not change with duration of disease up to 24 years. Treatment with L-dopa did not cause progressive reduction in receptor density. The diminished clinical response in the final stages of Parkinson's disease is not due to receptor dropout, and must depend on other factors.