(1/50) Striatal preproenkephalin gene expression is upregulated in acute but not chronic parkinsonian monkeys: implications for the contribution of the indirect striatopallidal circuit to parkinsonian symptomatology.

This study examined the extent of striatal dopamine (DA) denervation and coincident expression of preproenkephalin (PPE) mRNA in monkeys made parkinsonian by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) administration. Some animals (n = 4) became moderately parkinsonian after receiving large doses of MPTP over short periods of time and were symptomatic for only a short period of time (1-3 months; acute parkinsonian group). Other animals became moderately parkinsonian after receiving either escalating doses of MPTP over long periods (4-6 months; n = 5) or a high dose of MPTP over a short period (<1 month; n = 1) and remained symptomatic for an extended period (>8 months; chronic parkinsonian group). Despite similar symptomatology and similar degrees of striatal DA denervation at the time of their deaths, only acute parkinsonian animals had significantly increased PPE expression in sensorimotor striatal regions. PPE expression in chronic parkinsonian animals was either not changed or significantly decreased in most striatal regions. These findings suggest that the duration and not the extent of striatal DA denervation is a critical factor in modulating changes in striatal PPE expression. Furthermore, these results question the role of increased activity in the enkephalin-containing indirect striatopallidal pathway in the expression of parkinsonian symptoms.  (+info)

(2/50) Striatal dopaminergic markers in dementia with Lewy bodies, Alzheimer's and Parkinson's diseases: rostrocaudal distribution.

Dementia with Lewy bodies (DLB) is a neuropsychiatric disease associated with extrapyramidal features which differ from those of Parkinson's disease, including reduced effectiveness of L-dopa and severe sensitivity reactions to neuroleptic drugs. Distinguishing Alzheimer's disease from DLB is clinically relevant in terms of prognosis and appropriate treatment. Dopaminergic activities have been investigated at coronal levels along the rostrocaudal striatal axis from a post-mortem series of 25 DLB, 14 Parkinson's disease and 17 Alzheimer's disease patients and 20 elderly controls. [(3)H]Mazindol binding to the dopamine uptake site was significantly reduced in the caudal putamen in DLB compared with controls (57%), but not as extensively as in Parkinson's disease (75%), and was unchanged in Alzheimer's disease. Among three dopamine receptors measured (D1, D2 and D3), the most striking changes were apparent in relation to D2. In DLB, [(3)H]raclopride binding to D2 receptors was significantly reduced in the caudal putamen (17%) compared with controls, and was significantly lower than in Parkinson's disease at all levels. D2 binding was significantly elevated at all coronal levels in Parkinson's disease compared with controls, most extensively in the rostral putamen (71%). There was no change from the normal pattern of D2 binding in Alzheimer's disease. The only significant alteration in D1 binding ([(3)H]SCH23390) in the groups examined was an elevation (30%) in the caudal striatum in Parkinson's disease. There were no differences in D3 binding, measured using [(3)H]7-OH-DPAT, in DLB compared with controls. A slight, significant decrease in D3 binding in the caudal striatum of Parkinson's disease (13%) patients and an increase in Alzheimer's disease (20%) in the dorsal striatum at the level of the nucleus accumbens were found. The concentration and distribution of dopamine were disrupted in both DLB and Parkinson's disease, although in the caudate nucleus the loss of dopamine in DLB was uniform whereas in Parkinson's disease the loss was greater caudally. In the caudal putamen, dopamine was reduced by 72% in DLB and by 90% in Parkinson's disease. The homovanillic acid : dopamine ratio, a metabolic index, indicated compensatory increased turnover in Parkinson's disease, which was absent in DLB despite the loss of substantia nigra neurons (49%), dopamine and uptake sites. These differences between DLB, Parkinson's disease and Alzheimer's disease may explain some characteristics of the extrapyramidal features of DLB and its limited response to L-dopa and severe neuroleptic sensitivity. The distinct changes in the rostrocaudal pattern of expression of dopaminergic parameters are relevant to the interpretation of the in vivo imaging and diagnosis of DLB.  (+info)

(3/50) Recovery of dopamine neuronal transporter but lack of change of its mRNA in substantia nigra after inactivation by a new irreversible inhibitor characterized in vitro and ex vivo in the rat.

1. In vitro, the ability of DEEP-NCS {1-[2-(diphenylmethoxy)ethyl]-4-[2-(4-isothiocyanatophenyl)ethyl]- piperazine} to inhibit [3H]-dopamine uptake by rat striatal synaptosomes was concentration-dependent and inversely related to the protein concentration. This inhibition was irreversible and resulted from changes in Vmax and KM. DEEP-NCS was less potent on noradrenaline, serotonin and choline transport. 2. One day after intrastriatal injections of DEEP-NCS (100 and 1000 pmol) in 20% dimethylsulphoxide, moderate decreases in the ex vivo dopamine uptake were observed in synaptosomes obtained from striatum injected with DEEP-NCS or solvent, and the contralateral uninjected striatum. 3. In similar conditions, 300 pmol DEEP-NCS in 45% 2 hydroxypropyl-gamma-cyclodextrin - 0.5% dimethylsulphoxide solution sub-totally reduced ex vivo dopamine uptake and mazindol binding, and moderately decreased choline and serotonin transport. These reductions were specific to DEEP-NCS-injected striata. A clomipramine pretreatment (16 mg kg-1 i.p. 1 h before) was performed in following experiments, since it reduced the DEEP-NCS-elicited decrease in serotonin uptake without affecting other indices. 4. One day after intrastriatal injection, DEEP-NCS elicited similar dose-dependent decreases in ex vivo dopamine uptake and mazindol binding (ID50=6.9-8 ng striatum-1). Changes in KM and Vmax for ex vivo dopamine transport produced by DEEP-NCS disappeared according to similar time-courses. 5. The t(1/2) for transporter recovery was 6. 1 days. This value should correspond to its actual turnover rate in vivo, since no change in transporter mRNA level was observed in substantia nigra ipsilateral to 300 pmol DEEP-NCS-injected striatum. 6. The results indicate that DEEP-NCS behaves as a potent, quite selective, irreversible inhibitor of the DAT, in vitro and in vivo. Its use in vivo suggests that the physiological half-life of the rat striatal DAT is close to 6 days.  (+info)

(4/50) LLC-PK(1) cells stably expressing the human norepinephrine transporter: A functional model of carrier-mediated norepinephrine release in protracted myocardial ischemia.

In myocardial ischemia, adrenergic terminals undergo ATP depletion, hypoxia, and intracellular pH reduction, causing the accumulation of axoplasmic norepinephrine (NE) and intracellular Na(+) [via the Na(+)-H(+) exchanger (NHE)]. This forces the reversal of the Na(+)- and Cl(-)-dependent NE transporter (NET), triggering massive carrier-mediated NE release and, thus, arrhythmias. We have now developed a cellular model of carrier-mediated NE release using an LLC-PK(1) cell line stably transfected with human NET cDNA (LLC-NET). LLC-NET cells transported [(3)H]NE and [(3)H]N-methyl-4-phenylpyridinium ([(3)H]MPP(+)) in an inward direction. This uptake was abolished by the NET inhibitors desipramine (100 nM) and mazindol (300 nM) and by extracellular Na(+) removal. Na(+)-gradient reversal induced an efflux of (3)H-substrate from preloaded LLC-NET cells. Desipramine and mazindol blocked this efflux. Because of its greater intracellular stability and higher sensitivity to Na(+)-gradient reversal, [(3)H]MPP(+) proved preferable to [(3)H]NE as an NET substrate; therefore, only [(3)H]MPP(+) was used for subsequent studies. The K(+)/H(+) ionophore nigericin (10 microM) evoked a large efflux of [(3)H]MPP(+). This efflux was potentiated by the Na(+),K(+)-ATPase inhibitor ouabain (100 microM), was sensitive to desipramine, and was blocked by the NHE inhibitor 5-(N-ethyl-N-isopropyl)-amiloride (EIPA; 10 microM). In contrast, EIPA failed to inhibit the [(3)H]MPP(+) efflux elicited by the Na(+) ionophore gramicidin (10 microM). Furthermore, [(3)H]MPP(+) efflux induced by the NHE-stimulant proprionate (25 mM) was negatively modulated by imidazoline receptor activation. Our findings suggest that LLC-NET cells are a sensitive model for studying transductional processes of carrier-mediated NE release associated with myocardial ischemia.  (+info)

(5/50) Delayed onset of pulmonary hypertension associated with an appetite suppressant, mazindol: a case report.

The use of the appetite suppressant agents aminorex and fenfluramine derivatives has been reported as a risk factor for the development of pulmonary hypertension. A 29-year-old female developed pulmonary hypertension suspected to be due to an amphetamine-like appetite suppressant agent, mazindol ((+/-)-5-(p-chlorophenyl)-2,5-dihydro-3H-imidazo [2,1-a] isoindol-5-ol). She was admitted to Sapporo Medical University Hospital with dyspnea due to severe pulmonary hypertension. Twelve months prior to admission, she had taken mazindol continuously for a period of 10 weeks. As yet, her pulmonary hypertension has not completely improved. This is the first reported case of mazindol-associated pulmonary hypertension, which developed after a long latent interval, and it suggests that mazindol is also a risk factor for the development of pulmonary hypertension, making long-term follow-up necessary for patients taking this anorectic agent.  (+info)

(6/50) Amphetamine-induced loss of human dopamine transporter activity: an internalization-dependent and cocaine-sensitive mechanism.

The dopamine transporter (DAT) is a target of amphetamine (AMPH) and cocaine. These psychostimulants attenuate DAT clearance efficiency, thereby increasing synaptic dopamine (DA) levels. Re-uptake rate is determined by the number of functional transporters at the cell surface as well as by their turnover rate. Here, we present evidence that DAT substrates, including AMPH and DA, cause internalization of human DAT, thereby reducing transport capacity. Acute treatment with AMPH reduced the maximal rate of [(3)H]DA uptake, decreased AMPH-induced currents, and significantly redistributed the immunofluorescence of an epitope-tagged DAT from the plasma membrane to the cytosol in human embryonic kidney 293 cells. Conversely, DAT inhibitors, such as cocaine, mazindol, and nomifensine, when administered with AMPH, blocked the reduction in [(3)H]DA uptake and the redistribution of DAT immunofluorescence to the cytosol. The reductions of [(3)H]DA uptake and AMPH-induced DAT internalization also were inhibited by coexpression of a dominant negative mutant of dynamin I (K44A), indicating that endocytosis modulates transport capacity, likely through a clathrin-mediated pathway. With this mechanism of regulation, acute application of AMPH would reduce DA uptake not only by direct competition for uptake, but also by reducing the available cell-surface DAT. Moreover, AMPH-induced internalization might diminish the amount of DAT available for DA efflux, thereby modulating the cytotoxic effects of elevated extracellular DA.  (+info)

(7/50) Mazindol treatment of negative symptoms.

Hypodopaminergic and hyponoradrenergic pathophysiology may be a basis for primary and/or secondary negative symptoms in schizophrenia. The hypothesis that enhanced neurotransmission in these systems would be therapeutic for negative symptoms was tested by comparing mazindol and placebo in a double-blind, cross-over design trial. Outcome following mazindol supplementation was comparable to placebo supplementation (F(1,30) = 0.9; p = .57). Results for deficit and non-deficit schizophrenia subjects were similar, and were not affected by whether concurrent the antipsychotic drug treatment was clozapine, fluphenazine, or haloperidol. The efficacy hypothesis was not supported for either primary or secondary negative symptoms.  (+info)

(8/50) Role of 5-HT(2a) and 5-HT(2B/2C) receptors in the behavioral interactions between serotonin and catecholamine reuptake inhibitors.

Dysfunction of monoamine neurotransmission seems to contribute to such pathopsychological states as depression, schizophrenia, and drug abuse. The present study examined the effects of the selective serotonin (5-hydroxytryptamine; 5-HT) reuptake inhibitor (SSRI) and antidepressant fluvoxamine on locomotor activity in rats following administration of the catecholamine reuptake inhibitor mazindol. Mazindol (1 mg/kg) did not alter locomotor activity; whereas, fluvoxamine (20 mg/kg) given alone induced a brief period of hypomotility. Hyperactivity was elicited in a dose-related manner when fluvoxamine (5-20 mg/kg) was combined with mazindol (1 mg/kg). The hyperactivity elicited by fluvoxamine (20 mg/kg) plus mazindol (1 mg/kg) was significantly attenuated by the 5-HT(2A) receptor antagonist M100907 (2 mg/kg) and potentiated by the 5-HT(2B/2C) receptor antagonist SB 206553 (2 mg/kg). Neither antagonist significantly altered basal activity. The hyperactivity evoked by the combination of fluvoxamine and mazindol seems to be mediated in part by 5-HT(2A) receptors; whereas, 5-HT(2B/2C) receptors may serve to limit this effect. Thus, the balance of activation between 5-HT(2A) and 5-HT(2B/2C) receptors seems to contribute to the expression of locomotor hyperactivity evoked via combination of a 5-HT and a catecholamine reuptake inhibitor. A disruption in this balance may contribute to the expression of affective disorders, schizophrenia, and drug abuse.  (+info)