Transferrin receptor regulation in Parkinson's disease and MPTP-treated mice.
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1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗
Biomedical subjects
D C Mash
Publications and source records attributed to D C Mash.
Inactivation of human immunodeficiency virus-1 at short time intervals using undiluted bleach.
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Cell Survival↗
Differential cholinergic innervation within functional subdivisions of the human cerebral cortex: a choline acetyltransferase study.
The distribution of cholinergic fibers in the human brain was investigated with choline acetyltransferase immunocytochemistry in 35 cytoarchitectonic subdivisions of the cerebral cortex. All cortical areas and all cell layers contained cholinergic axons. These fibers displayed numerous varicosities and, on occasion, complex preterminal profiles arranged in the form of dense clusters. The density of cholinergic axons tended to be higher in the more superficial layers of the cerebral cortex. Several distinct patterns of lamination were identified. There were also major differences in the overall density of cholinergic axons from one cytoarchitectonic area to another. The cholinergic innervation of primary sensory, unimodal, and heteromodal association areas was lighter than that of paralimbic and limbic areas. Within unimodal association areas, the density of cholinergic axons and varicosities was significantly lower in the upstream (parasensory) sectors than in the downstream sectors. Within paralimbic regions, the non-isocortical sectors had a higher density of cholinergic innervation than the isocortical sectors. The highest density of cholinergic axons was encountered in core limbic structures such as the hippocampus and amygdala. These observations show that the cholinergic innervation of the human cerebral cortex displays regional variations that closely follow the organization of information processing systems.
Adult↗
Sigma receptors are associated with cortical limbic areas in the primate brain.
Putative sigma receptors are a current target for antipsychotic drug development. Novel antipsychotic agents which possess selective and high affinity for sigma binding sites may serve as an alternative to the principal neuroleptic drugs currently in clinical use which mediate extrapyramidal side effects and dyskinesias through their blockade of dopamine receptors. We have used in vitro autoradiography to localize putative sigma receptors labelled with (+)-[3H]-3-(3-hydroxyphenyl)-N-(1-propyl)piperidine [(+)-[3H]-3-PPP] in the brain of the rhesus macaque. The binding characteristics of (+)-[3H]-3-PPP in the primate brain were comparable to those previously described in the rodent. Saturation analysis demonstrated a single class of sites in cerebellar and hippocampal membranes with a Kd value of 28 nM. Sigma receptors labeled with (+)-[3H]-3-PPP in the primate brain displayed the appropriate rank order of potency and stereoselectivity in competition binding assays. Haloperidol displaced (+)-[3H]-3-PPP binding in the low nanomolar range, and the (+) isomer of pentazocine was 50-fold more potent than (-) pentazocine. Computerized densitometric analysis of the autoradiograms demonstrated a striking enrichment of sigma binding sites over the paralimbic belt cortices, including the orbitofrontal, cingulate, insular, parahippocampal, and temporopolar gyri. Peak densities of sigma receptors were seen over the medial and central nuclei of the amygdala and were widely distributed within the hippocampal formation. Sigma binding sites densities were elevated over the suprachiasmatic and supraoptic nuclei of the hypothalamus. Moderate sigma receptor densities were observed over the ventromedial sectors of the caudate and the putamen. Sigma receptors were also elevated over autonomic relay nuclei of the brainstem, including the nucleus of the solitary tract and the dorsal motor nucleus of the vagus. The distribution of sigma receptors in the primate brain suggests that the paralimbic belt cortices, amygdala, hippocampus, hypothalamus, and autonomic relay nuclei of the brainstem may be interrelated by a topographic chemical linkage. The autoradiographic visualization of sigma receptor distributions in the primate brain provides further support for a role of sigma receptor mechanisms in the functions of the limbic system.
Animals↗
Comparison of the concentration of messenger RNA encoding four muscarinic receptor subtypes in control and Alzheimer brains.
We determined the concentration of the messenger RNA species which encode four (m1-m4) of the five cloned muscarinic receptors in brains of Alzheimer's disease patients as compared to age-matched controls. Assays were performed using the quantitative method of DNA-excess solution hybridization in the cerebral cortex (frontal, temporal and occipital), hippocampus, nucleus basalis of Meynert and brainstem. The results suggest a statistically significant decrease in the m1 muscarinic receptor message in the temporal and occipital cortex, with no change in other regions. There was no change in the level of mRNA encoding the m2, m3 or m4 receptors in any of the brain regions studied.
Aged↗
21-aminosteroids interact with the dopamine transporter to protect against 1-methyl-4-phenylpyridinium-induced neurotoxicity.
U-78518F, a 21-aminosteroid from the novel family of lipid peroxidation inhibitors (lazaroids), increased survival of dopamine (DA) neurons in mesencephalic cell cultures incubated with the neurotoxin 1-methyl-4-phenylpyridinium (MPP+). Protection against DA neuron death occurred with increasing concentrations of U-78518F up to 30 microM. Non-specific toxicity produced with higher concentrations of MPP+ was not affected by the lazaroid. U-78518F inhibited cellular uptake of [3H]MPP+ and [3H]DA, but not that of gamma-[3H]aminobutyric acid. In human striatal membrane preparations, U-78518F competed with [3H]mazindol for binding to the DA transporter, with a calculated Ki value of 10 microM. Two of four lazaroids tested inhibited [3H]DA uptake in the cell culture system. The protective effects of 21-aminosteroids in MPP(+)-induced neurotoxicity are, in part, a function of the interaction of these agents with the DA transporter.
1-Methyl-4-phenylpyridinium↗
Interactions of cocaine with primary and secondary recognition sites on muscarinic receptors.
Several lines of evidence have suggested that muscarinic receptors may possess more than one ligand binding site. In this study, the interactions of cocaine with primary and secondary (allosteric) sites on muscarinic receptors in membrane homogenates from post-mortem human brainstem were examined. (-)-Cocaine inhibited the binding of the tritiated muscarinic antagonists N-methylscopolamine (NMS) and pirenzepine to an apparent single class of sites, with Ki values of 200-300 microM. The binding of the muscarinic agonist [3H]oxotremorine-M was inhibited with a similar Ki value (200 microM). (+)-Cocaine, although not the naturally occurring stereoisomer, was 10-20-fold more potent than (-)-cocaine in competing for binding to the primary muscarinic recognition site. The binding of cocaine was unaffected by guanine nucleotides or N-ethylmaleimide, consistent with its purported action as a competitive antagonist. Cocaine was not selective for muscarinic receptor subtypes. Rosenthal analysis of the [3H]NMS saturation binding data in the presence of increasing concentrations of either (-)-cocaine or (+)-cocaine indicated that both isomers produced an apparent competitive-like reduction in the [3H]NMS affinity. Schild regression analysis of the saturation binding data resulted in curvilinear plots suggestive of cooperative or allosteric interactions of (-)-cocaine with the [3H]NMS-labeled receptors. The effects of (-)-cocaine on the kinetics of [3H]NMS binding were consistent with an allosteric interaction with the receptor. Increasing concentrations of cocaine markedly slowed the rate of [3H]NMS dissociation from the primary recognition site. The allosteric modulation of [3H] NMS binding by (-)-cocaine was abolished with increasing ionic strength. Taken together, these data demonstrate that (-)-cocaine interacts with primary and allosteric recognition sites on muscarinic receptors.
Adult↗
Loss of high-affinity agonist binding to M1 muscarinic receptors in Alzheimer's disease: implications for the failure of cholinergic replacement therapies.
Cholinergic replacement therapies have yielded little or no clinical improvement in Alzheimer's disease (AD). Since the number of postsynaptic muscarinic receptors remains unchanged in the cerebral cortex, the involvement of other neurotransmitter systems may account for this limited efficacy. Alternatively, there may be a defective coupling of the muscarinic receptor with its nucleotide-binding protein in AD, which would severely limit the ability of cholinergic agonists to activate intracortical second messengers. To address this possibility, we assessed the ability of the putative M1 muscarinic receptor to form high-affinity agonist-receptor complexes with guanine nucleotide regulatory proteins in postmortem frontal cortex. Agonist affinity states of the M1 muscarinic receptor were measured by carbachol/[3H]-pirenzepine competition. M1 muscarinic receptors exhibited both high (KH) and low (KL) affinities for the agonist carbachol. High-affinity agonist binding to M1 receptors in postmortem frontal cortex samples from subjects with AD was reduced, demonstrated by an increase in the KH value. Low-affinity agonist binding (KL value) was unchanged in AD and was not significantly different from the KL value for the uncoupled receptor determined in the presence of guanine nucleotides. The increase in the KH value resulted in a 70% decrease in the average KL/KH ratio for AD as compared to control samples. Choline acetyltransferase activities correlated significantly with the KL/KH ratios (r = 0.73, p less than 0.001). These data suggest that the KL/KH ratio for muscarinic agonists may serve as a neurochemical marker of disease severity. The reduced ability of the M1 receptor subtype to form a high-affinity agonist state in AD may account for the failure of cholinergic replacement therapies to improve specific features of memory and cognition.
Aged↗
Distribution and number of transferrin receptors in Parkinson's disease and in MPTP-treated mice.
Transferrin is a glycoprotein that functions primarily to deliver iron to the cell. Recent studies suggest that the transferrin receptor mediates the intracellular delivery and transport of iron bound to transferrin in the CNS. Iron-catalyzed free radical generation has been proposed as a possible cause of nigral cell death in Parkinson's disease. Our hypothesis is that abnormal iron handling by the transferrin receptor may contribute to the formation of free radical species which catalyze the lipid peroxidation of nigral cell membranes. We have assessed the number of transferrin receptors on membrane fractions prepared from the human striatum from control subjects and patients with Parkinson's disease. Equilibrium-binding studies demonstrated a reversible, saturable, and high-affinity transferrin binding site (KD = 3 nM) in human brain membranes. Regional binding assays indicate that the number of transferrin receptors in the putamen was reduced significantly in Parkinson's disease. The density of transferrin receptors was unaltered in membranes prepared from the caudate nuclei and the globus pallidus. To address the possibility that transferrin receptors are located on dopaminergic terminals, we have examined the distribution and number of transferrin receptors in the striatum of MPTP-treated mice using in vitro autoradiographic methods. In these experiments, the loss of dopaminergic terminals in the striatum was visualized by differential [3H]mazindol uptake site autoradiography. A marked reduction in the density of both transferrin receptors and [3H]mazindol binding sites was observed in the mouse striatum 7 days post-MPTP treatment.(ABSTRACT TRUNCATED AT 250 WORDS)
1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗
Cocaethylene is more potent than cocaine in mediating lethality.
Cocaethylene is a pharmacologically active cocaine metabolite that is formed in the presence of ethanol by the activity of liver enzymes. The pharmacology of cocaethylene has not been extensively investigated and its acute toxicity is unknown. The acute toxicity of cocaethylene was compared to cocaine in Swiss-Webster mice. The LD50 of cocaethylene was 60.7 mg/kg and 63.8 mg/kg in female and male mice, respectively. In comparison, the LD50 of cocaine was 93.0 mg/kg in both female and male mice. These studies demonstrate that the cocaine-alcohol metabolite, cocathylene, is more potent in mediating lethality than the parent drug.
Animals↗
Cocaethylene: a unique cocaine metabolite displays high affinity for the dopamine transporter.
Concurrent cocaine and alcohol use is common practice in the general population, as indicated by recent prevalence studies. In the presence of ethyl alcohol, cocaine is metabolized to its ethyl homolog, cocaethylene. The transesterification of cocaine and ethanol to cocaethylene takes place in the liver and represents a novel metabolic reaction. Cocaethylene was detected in postmortem blood, liver, and neurological tissues in concentrations equal to and sometimes exceeding those of cocaine. In vitro binding studies demonstrate that cocaethylene has a pharmacological profile similar but not identical to that of cocaine at monoamine transport sites assayed in the human brain. Cocaethylene was equipotent to cocaine at inhibiting [3H]mazindol binding to the dopamine transporter. The blockade of dopamine reuptake in the synaptic cleft by cocaethylene may account for the enhanced euphoria associated with combined alcohol and cocaine abuse.
Adult↗
Pargyline-sensitive selective accumulation of a radiolabeled MPTP analog in the primate cerebral cortex and basal ganglia.
The distribution of radioiodinated N-methyl-4-(4-hydroxy-3-iodobenzyl)-1,2,3,6-tetrahydropyridine (MHTP), an analog of the reportedly nontoxic N-methyl-4-benzyl-1,2,3,6-tetrahydropyridine, (4-homo-MPTP), has been studied in the primate. [123I]MHTP-derived radioactivity exhibited a progressive accumulation and prolonged retention within the primate eye. Following iv injection, [123I]MHTP rapidly accumulated within the primate brain and was subsequently oxidized to a radiolabeled metabolite. The half-life of [123I]MHTP-derived radioactivity within the primate brain was 50 min. The highest concentrations of radioactivity were found in the caudate-putamen and the frontal, temporal and cingulate cortices; the substantia nigra and inferior olivary nucleus were labeled with medium intensity. Very low concentrations of radiolabel were detected in the cerebellum and white matter. Selective accumulation of [125I]MHTP-derived radioactivity within these structures was blocked by pretreatment with pargyline, suggesting that monoamine oxidase B is involved in the bioactivation of radioiodinated MHTP.
1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗
Characterization and distribution of transferrin receptors in the rat brain.
Transferrin receptors were characterized with 125I-ferrotransferrin on membrane fractions prepared from the rodent forebrain. The distribution of transferrin receptors in the rat brain was investigated further by in vitro autoradiography. Saturation binding analysis revealed an apparent single class of sites with a dissociation constant of 2 nM and a binding site density of 15 pmol/g. The Hill coefficient derived from these data was 1.05, indicating the absence of cooperativity and that 125I-ferrotransferrin binds to a single class of sites. Estimates of the kinetically determined KD for forebrain membranes were within the 2-4 nM range, in agreement with the equilibrium measurements. Apotransferrin and ferrotransferrin competitively displaced the binding of 125I-ferrotransferrin, while ferritin, albumin, and cytochrome c failed to compete for the binding site. Ceruloplasmin, the copper transport protein, was a weak inhibitor of 125I-ferrotransferrin binding. Autoradiographic localization studies demonstrate a heterogeneous distribution of transferrin receptors in the rat brain. Transferrin receptor densities were markedly elevated over the cerebral cortex and the hippocampus. Moderate to high 125I-ferrotransferrin binding was also apparent throughout areas involved in motor functions, including the caudate-putamen, the nucleus accumbens, the substantia nigra, the red nucleus, and the cerebellum.
Animals↗
Multiple in vitro interactions with and differential in vivo regulation of muscarinic receptor subtypes by tetrahydroaminoacridine.
Tetrahydroaminoacridine (THA) is known to be a potent centrally acting cholinesterase inhibitor. In this report, the effects of THA in vivo and in vitro on the binding of muscarinic agonists and antagonists to putative M1 and M2 receptor subtypes were assessed in rat brain membranes. THA competitively inhibited labeled agonist and antagonist binding to membranes prepared from M1 and M2 enriched brain regions. The dissociation of radiolabeled antagonists from muscarinic receptors was decelerated markedly by THA. The half-time for dissociation of [3H]oxotremorine-M from the high affinity state of M1 and M2 receptors was unaffected by THA. Chronic THA administration resulted in a selective down regulation in the number of M1 receptors assayed directly with the M1-selective antagonist, [3H]pirenzepine. The decrease in the binding capacity of [3H]pirenzepine was correlated positively with the duration of drug treatment. Saturation analysis of [3H]pirenzepine binding confirmed that this loss in binding capacity was due to a reduction in the number of binding sites and not an altered affinity of the receptor for [3H]pirenzepine. Carbachol-[3H]pirenzepine competition revealed no change in the ratio of high and low affinity agonist states of the M1 receptor with chronic THA administration. In vivo studies demonstrate further that the total number of muscarinic receptors was decreased significantly, whereas putative M2 receptors, measured directly with the agonist [3H]oxotremorine-M or estimated by pirenzepine-[3H]quinuclidinyl benzilate competition, were unchanged. Thus, THA exhibits multiple actions at primary and secondary recognition sites on putative M1 and M2 subclasses of muscarinic receptors. The results suggest further that the clinical pharmacology of THA may represent a composite efficacy of THA at multiple sites on cholinergic synapses.
Allosteric Regulation↗
Distribution of muscarinic receptor subtypes within architectonic subregions of the primate cerebral cortex.
The regional distributions of muscarinic receptor subtypes (M1 and M2) in the macaque brain were investigated by in vitro receptor autoradiography. Putative muscarinic receptor subtypes were distinguished by their differential affinities for pirenzepine and carbachol in competition with [3H]-quinuclidinyl benzilate. Autoradiographic visualization of muscarinic receptor subtypes demonstrated marked regional and laminar variations that respected architectonic boundaries. The M1 receptor subtype was widely distributed throughout most cortical areas and was most intense over the superficial layers. Almost all limbic and paralimbic regions including the amygdala, hippocampus, orbitofrontal, temporopolar, parahippocampal, cingulate, and parolfactory areas displayed peak densities of the M1 receptor subtype. The M2 receptor subtype was selectively elevated in the primary sensory areas of all five sensory modalities, including the visual (area 17, V1), auditory (A1), and somatosensory (3b, S1) koniocortices, the anterior olfactory nucleus, and the gustatory area. The primary motor area also displayed a relative peak of M2 receptor subtype labeling. In the hippocampal formation, M1, M2, and nicotine receptors were distributed differentially, with each subdivision having a specific complement of cholinergic receptor subtype. The M1 receptor subtype was prevalent in the dentate gyrus, the CA4-CA3 region, and the CA1 ammonic sector. The M2 receptor subtype was concentrated in the CA2 sector, the subiculum, the rhinal cortices, and the parasubiculum. Putative neural nicotinic receptors, tagged with L-[3H]-nicotine, were most concentrated within the presubiculum.
Animals↗
Neurofibrillary tangles in cholinergic pedunculopontine neurons in Alzheimer's disease.
The cholinergic neurons located within the pedunculopontine nucleus (Ch5) of patients with Alzheimer's disease (AD; n = 15), Parkinson's disease (PD; n = 2), and neurologically normal (n = 6) subjects were visualized immunohistochemically using choline acetyltransferase, pharmacohistochemically using acetylcholinesterase, or by reduced histochemical methods using nicotinamide adenine dinucleotide phosphate diaphorase (NADPH-d). Each histochemical procedure localized a well-delineated, compact lateral group and a more diffuse medial group of neurons within the pedunculopontine nucleus. Co-localization experiments revealed that all three enzymes marked the same population of cholinergic neurons. The extent of pathological alterations associated with the cholinergic neurons within the compact lateral sector of the pedunculopontine nucleus was examined in sections that reacted for NADPH-d, counterstained with thioflavin-S. The average number of neurofibrillary tangles within this portion of the pedunculopontine nucleus was 25.4 (range 0-70) in patients with AD, 1.5 (range 1-2) in those with PD, and 1.2 (range 0-4) in aged control subjects. Of the total number of neurofibrillary tangles counted in AD cases, 72.7% were end-stage ghosts and 27.3% were tangle-bearing neurons. The pathological alteration of cholinergic neurons of the compact lateral aspect of the pedunculopontine nucleus may play a role in some of the behavioral features characteristic of AD.
Acetylcholinesterase↗
Localization of nerve growth factor receptors in cholinergic neurons of the human basal forebrain.
Nerve growth factor (NGF) receptors were visualized in the basal human forebrain using an immunohistochemical procedure with a monoclonal antibody previously shown to recognize human melanoma cell NGF receptors. The receptors were found to be exclusively located in the medical septal nucleus, the diagonal band of Broca, and the nucleus basalis. This location coincided with that of cell bodies of ascending cholinergic neurons of the basal forebrain. In addition, NGF receptor-positive cells were costained for acetylcholinesterase. These findings indicate that cholinergic neurons of the basal forebrain but none of the other neurons located in this area express receptors for NGF. Results suggest that NGF acts as a trophic factor for cholinergic neurons in the human brain in a similar way as has been established in recent years for the rat brain.
Acetylcholinesterase↗
Cholinergic projections from the parabigeminal nucleus (Ch8) to the superior colliculus in the mouse: a combined analysis of horseradish peroxidase transport and choline acetyltransferase immunohistochemistry.
Choline acetyltransferase (ChAT) immunocytochemistry, acetylcholinesterase histochemistry and muscarinic receptor autoradiography demonstrated a cholinergic innervation within the superior colliculus. A method for the concurrent visualization of ChAT and transported horseradish peroxidase showed that a major extrinsic source for this cholinergic input is in the parabigeminal nucleus. We have designated these cholinergic neurons as the Ch8 cell group.
Acetylcholinesterase↗