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F Fornai

Publications and source records attributed to F Fornai.

At least 19 recordsLinked to original sources
PubMed2002

Continuous subcutaneous infusion of apomorphine rescues nigro-striatal dopaminergic terminals following MPTP injection in mice.

Apomorphine has been introduced in the treatment of late-stage Parkinson's Disease (PD). The disadvantage of a short half-life of apomorphine is now overcome by the use of a continuous subcutaneous (s.c.) self-delivering system. We examined whether continuous s.c. infusion of apomorphine rescues nigro-striatal dopaminergic neurons from toxicity induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) in mice. Apomorphine was continuously infused in mice by means of a s.c. minipump that delivered the drug at a rate of 0.5 or 3.15 mg/kg/day. MPTP induced a >80% reduction in striatal dopamine (DA) after one day. DA levels were still substantially reduced one month following MPTP injection, in spite of a partial recovery. Similarly, striatal immunoreactivity for tyrosine hydroxylase and dopamine transporter was markedly reduced at this time interval. Continuous s.c. infusion of apomorphine starting 40 h following MPTP injection rescued striatal dopaminergic terminals, as assessed by measurements of DA and its metabolites, as well as TH and DAT immunostaining after one month. The neurorescuing effect was more remarkable at a delivery rate of 3.15 mg/kg/day of apomorphine. In contrast, no rescue was observed when apomorphine was administered as a single daily s.c. bolus of 1 or 5mg/kg starting 40 h following MPTP. We conclude that apomorphine is able to rescue nigro-striatal dopaminergic neurons when continuously delivered at doses that are comparable to those delivered by minipumps in PD patients. These results suggest that continuous s.c. infusion of apomorphine not only relieves the symptoms, but also reduce the ongoing degeneration of nigro-striatal dopaminergic neurons in PD patients.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗
PubMed2002

Morphological and biochemical evidence that apomorphine rescues striatal dopamine terminals and prevents methamphetamine toxicity.

Apomorphine, given by a single injection, repeated injections, or by continuous infusion, was tested for neuroprotective effects in mice administered methamphetamine or N-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) in order to induce striatal dopamine (DA) depletion. In the first part of the study, the DA agonist (R)-apomorphine was administered at various doses (1, 5, and 10 mg/kg), 15 min before methamphetamine (5 mg/kg x 3, 2 h apart). Mice were sacrificed 5 days later. In the second part, apomorphine was administered either continuously by subcutaneous minipump (cumulative daily dose of 0.5, 1, and 3.15 mg/kg), or as single, repeated daily injections (up to 5 mg/kg) starting 40 h after an acute administration of MPTP (30 mg/kg). Mice were sacrificed at different time intervals (up to 1 month) following MPTP injection. In all the animals, the integrity of striatal DA terminals was evaluated by measuring striatal DA levels and TH immunohistochemistry. Apomorphine dose-dependently prevented methamphetamine toxicity. These effects were neither due to a decrease in the amount of striatal methamphetamine nor to the hypothermia, and they were not reversed by the DA antagonist haloperidol. Moreover, chronic, continuous (but not pulsatile) administration of apomorphine rescued damaged striatal dopaminergic terminals. These findings confirm a protective effect of apomorphine that also consists of a neurorescue of damaged striatal DA terminals. This suggests a new hypothesis about the long-term benefits observed during continuous apomorphine administration in Parkinson's disease patients.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗
PubMed2002

Striatal postsynaptic ultrastructural alterations following methylenedioxymethamphetamine administration.

Amphetamine derivatives, such as methamphetamine (METH) and 3,4-methylenedioxymethamphetamine (MDMA), act as monoaminergic neurotoxins in the central nervous system. Although there are slight differences in their mechanism of action, these compounds share a final common pathway, which involves dopamine release and oxidative stress. Apart from striatal toxicity involving monoamine axons, no previous report evidenced any alteration at the striatal level concerning postsynaptic sites. Given the potential toxicity for extracellular dopamine at the striatal level, and the hypothesis for neurotoxic effects of dopamine on striatal medium-sized neurons in Huntington's disease, we evaluated at an ultrastructural level the effects of MDMA on intrinsic striatal neurons of the mouse. In this study, administering MDMA, we noted ultrastructural alterations of striatal postsynaptic GABAergic cells consisting of neuronal inclusions shaped as whorls of concentric membranes. These whorls stained for ubiquitin but not for synuclein and represent the first morphologic correlate of striatal postsynaptic effects induced by MDMA.

Animals↗
PubMed2001

Arginine:glycine amidinotransferase deficiency: the third inborn error of creatine metabolism in humans.

Arginine:glycine amidinotransferase (AGAT) catalyzes the first step of creatine synthesis, resulting in the formation of guanidinoacetate, which is a substrate for creatine formation. In two female siblings with mental retardation who had brain creatine deficiency that was reversible by means of oral creatine supplementation and had low urinary guanidinoacetate concentrations, AGAT deficiency was identified as a new genetic defect in creatine metabolism. A homozygous G-A transition at nucleotide position 9297, converting a tryptophan codon (TGG) to a stop codon (TAG) at residue 149 (T149X), resulted in undetectable cDNA, as investigated by reverse-transcription PCR, as well as in undetectable AGAT activity, as investigated radiochemically in cultivated skin fibroblasts and in virus-transformed lymphoblasts of the patients. The parents were heterozygous for the mutant allele, with intermediate residual AGAT activities. Recognition and treatment with oral creatine supplements may prevent neurological sequelae in affected patients.

Amidinotransferases↗
PubMed2001

Intrastriatal injection of D1 or D2 dopamine agonists affects glucose utilization in both the direct and indirect pathways of the rat basal ganglia.

Two distinct pathways are thought to connect the striatum to the basal ganglia output nuclei: a direct pathway, originating from neurons bearing dopamine, D(1) receptors and an indirect pathway, originating from neurons expressing D(2) receptors. It has been recently suggested, however, that dopamine receptor sub-types may co-localize and co-operate in the striatum. We sought to verify the functional segregation of the two pathways by measuring cerebral glucose utilization following intrastriatal injection of selective D(1) (SKF 38393), D(2) (quinpirole), or non-selective indirect (amphetamine) and direct (apomorphine) dopamine agonists, in freely-moving rats. All drugs -- regardless of receptor selectivity -- reduced glucose utilization in nuclei of both the direct and indirect pathways, thus lending further support to the existence of a functional co-operation of striatal D(1) and D(2) receptors.

2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-ben↗
PubMed2001

Dose-dependent protective effects of apomorphine against methamphetamine-induced nigrostriatal damage.

(R)-apomorphine is a non-selective dopamine (DA) agonist which is used in the treatment of Parkinson's disease. In addition to symptomatic effects, apomorphine exerts a neuroprotective activity in specific experimental models. For instance, apomorphine prevents experimental parkinsonism induced by the neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine. Neuroprotection obtained with apomorphine does not seem to be related to its dopamine (DA) agonist properties, instead it appears to be grounded on the antioxidant and the free radical scavenging effects of the compound. In this study, we sought to determine whether apomorphine protects against methamphetamine toxicity. We found that apomorphine (1; 5 and 10 mg/kg) dose-dependently protects against methamphetamine- (5 mg/kg X3, 2 h apart) induced striatal DA loss and reduction of tyrosine hydroxylase (TH) activity in the rat striatum. These protective effects are neither due to a decrease in the amount of striatal methamphetamine nor to hypothermia as indicated by measurement of striatal methamphetamine and body temperature at different time intervals after drug administration. The effects of apomorphine were neither opposite to, nor reversed by the DA antagonist haloperidol despite no decrease in body temperature was observed when apomorphine was given in combination with haloperidol. The present data are in line with recent studies suggesting a DA receptor-independent neuroprotective effect of apomorphine on DA neurons and call for further studies aimed at evaluating potential neuroprotective effects of apomorphine in Parkinson's disease.

Animals↗
PubMed2001

Biochemical effects of the monoamine neurotoxins DSP-4 and MDMA in specific brain regions of MAO-B-deficient mice.

Previous studies reported that drugs acting as monoamine oxidase (MAO)-B inhibitors prevented biochemical effects induced by the neurotoxins N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine (DSP-4) and 3,4-methylenedioxymethamphetamine (MDMA, "ecstasy"). In this study, we administered DSP-4 (50 mg/kg) or MDMA (50 mg/kg x 2, 2 h apart) to MAO-B deficient mice. Monoamine content in various brain regions (cerebellum, frontal cortex, hippocampus, hypothalamus, striatum, substantia nigra) was assayed 1 week after neurotoxin administration. Injection of DSP-4 to wild-type mice caused a marked norepinephrine (NE) loss in specific brain regions. Unexpectedly, DSP-4 caused similar effects in MAO-B-deficient and in wild-type mice in all brain regions investigated. These results suggest that MAO-B is not involved in DSP-4 toxicity. In wild-types, the neurotoxin MDMA induced both serotonin (5HT) and dopamine (DA) depletion in specific brain areas. In MAO-B-deficient mice, 5HT depletion observed in wild-types did not occur. In contrast, MDMA produced a more pronounced DA loss in knockout mice compared with wild-types. The present findings, together with previous data obtained using selective enzyme inhibitors, suggest that MAO-B is not involved in the mechanism of action of DSP-4, whereas it plays opposite roles in MDMA-induced DA and 5HT depletions.

Animals↗
PubMed2001

Sexual pheromone or conventional odors increase extracellular lactate without changing glucose utilization in specific brain areas of the rat.

Brain extracellular lactate levels increase following physiological stimuli. Monitoring lactate levels might be a tool for detecting dynamic changes in brain activity. In this study we compared changes of extracellular lactate in selected brain areas with rates of glucose utilization as measured by the [14C]2-deoxyglucose method, following olfactory stimulation. Conventional (green pepper essence, heptanal, exanal, octanal) and, above all, non-conventional (sexual pheromone) odors increased lactate in the rhinencephalum, but not in the striatum. Glucose utilization did not change in any area. This discrepancy may result from the different temporal resolution of the two methods employed and/or from the clearance of lactate, whose tissue content increases transiently following neuronal activation as a reflection of the initial oxygen debt.

Animals↗
PubMed2001

Proton magnetic resonance spectroscopic imaging reveals differences in spinocerebellar ataxia types 2 and 6.

The objective of this study was to investigate cerebellar metabolism in patients with autosomal dominant cerebellar ataxia type 1 (ADCA-I) carrying two distinct mutations of spinocerebellar ataxia (SCA). Non-invasive image-guided proton magnetic resonance spectroscopy imaging (1H-MRSI) was performed in 4 patients with SCA2, and 3 patients carrying the SCA6 mutation. For MRSI, we employed a spin-echo sequence (TR = 1500 msec, TE = 135 msec, slice thickness = 15 mm, FOV = 240 mm) and a stimulated-echo sequence (TR = 1500 msec, TE = 20 msec, slice thickness = 15 mm, FOV = 240 mm). Measures included the peak integral ratios of neuronal and glial markers [N-acetylaspartate (NA) to creatine (Cr), choline-containing compounds (CHO) to Cr, and lactate (LAC) to Cr]. We found NA:Cr ratios were significantly lower in patients with SCA2 (40.4% lower) compared to patients carrying the SCA6 mutation. CHO:Cr ratios differed between the two mutations using short echo time (30.8% lower in SCA2), but not when applying long echo time 1H-MRSI. Measurements using long echo time revealed LAC peaks in all SCA2 patients. 1H-MRSI revealed metabolic differences between SCA2 and SCA6 patients. NA:Cr ratios were significantly lower in patients with the SCA2 mutation compared to the SCA6 mutation, and LAC signals were obtained in the cerebella of SCA2 patients. In addition, CHO:Cr ratios showed different behavior using short and long TE, indicating differences in relaxation times of choline compounds in SCA2.

Adult↗
PubMed2001

Subcellular localization of a glutathione-dependent dehydroascorbate reductase within specific rat brain regions.

Recently, we described the occurrence of a dehydroascorbate reductase within the rat CNS. This enzyme regenerates ascorbate after it is oxidized during normal aerobic metabolism. In this work, we describe the neuronal compartmentalization of the enzyme, using transmission electron microscopy of those brain areas in which the enzyme was most densely present when observed under light microscopy. In parallel biochemical studies, we performed immunoblotting and measured the enzyme activity of the cytoplasm and different nuclear fractions. Given the abundance of ascorbate in the caudate-putamen, we focused mostly on the occurrence of dehydroascorbate reductase at the striatal subcellular level. We also studied cerebellar Purkinje cells, hippocampal CA3 pyramidal cells and giant neurons in the magnocellular part of the red nucleus. In addition to neurons, immunolabeling was found in striatal endothelial cells, in the basal membrane of blood vessels and in perivascular astrocytes. In neuronal cytosol, the enzyme was observed in a peri-nuclear position and on the nuclear membrane. In addition, in both the striatum and the cerebellum, we found the enzyme within myelin sheets. Dehydroascorbate reductase was also present in the nucleus of neurons, as further indicated by measuring enzyme activity and by immunoblotting selected nuclear fractions. Immunocytochemical labeling confirmed that the protein was present in isolated pure nuclear fractions. Given the great amount of free radicals which are constantly generated in the CNS, the discovery of a new enzyme with antioxidant properties which translocates into neuronal nuclei appears to be a potential starting point to develop alternative strategies in neuroprotection.

Animals↗
PubMed2001

Immunohistochemical evidence and ultrastructural compartmentalization of a new antioxidant enzyme in the rat substantia nigra.

We previously described in the rat the presence of dehydroascorbate reductase, an enzyme regenerating ascorbic acid, which is constantly lost during oxidative processes occurring at a fast rate within the central nervous system. In the present study, we specifically evaluate the occurrence of this enzyme in the rat substantia nigra by using immunohistochemistry, and by analyzing the neuronal compartmentalization of dehydroascorbate reductase within nigral neurons by immunoblotting and transmission electron microscopy coupled with immunocytochemistry. The enzyme occurs in various portions of the substantia nigra, but it is more abundant in the ventromedial part extending through the ventral tegmental area, and the dorsal portion, involving the pars compacta. Within nigral neurons, the cytosolic enzyme is present in a perinuclear position, close to mitochondria, and in the nuclear membrane; we also found the enzyme in nigral axons close to the myelin sheath. In addition, dehydroascorbate reductase was present in the nucleus of nigral neurons. The nuclear occurrence of the enzyme was confirmed by immunocytochemical labelling and immunoblotting of isolated nuclei. The nuclear enzyme was constantly evident as clusters of immunogold particles on chromatin. This localization suggests new roles for dehydroascorbate reductase (eg. prevention of DNA oxidative damage and regulation of gene transcription).

Animals↗
PubMed2001

Novel aspects of dopamine oxidative metabolism (confounding outcomes take place of certainties).

Abstract: Understanding dopamine (DA) oxidative metabolism allows to get a deeper insight into neurologic and psychiatric disorders featured by an altered DA neurotransmission as well as developing appropriate therapeutic strategies. Oxidative DA deamination is carried out by two highly conserved isoenzymes: monoamine oxidase (MAO) A and B; these isoenzymes both metabolize DA to dihydroxyphenylacetaldehyde (DOPALD), which, in turn, is converted to dihydroxyphenylacetic acid (DOPAC). In the past twenty years most studies on MAO activity were performed using brain dialysis in freely moving rats and measuring DA and DOPAC levels after administration of specific MAO inhibitors. This led to concepts on DA metabolism grounded on a single brain area (striatum) investigated, almost exclusively, in a single animal species (rat). These experiments were based on measurement of striatal levels of DOPAC which represents the indirect product of MAO activity. At present, the specific role of each MAO isoform appears to differ significantly depending on varying experimental conditions such as measuring the direct product of DA metabolism. In particular, recent studies allowed the estimate of the first metabolite (DOPALD) formed by MAO, showing that DOPAC levels do not necessarily reflect MAO activity. Again, the relative contribution of the two MAO iso forms in sustaining DA metabolism varies considerably, depending on the animal species and the specific brain area (either striatum or substantia nigra) under investigation. In this article we will briefly review these concepts in light of new evidence derived from innovative approaches: improved in vivo analysis of direct MAO metabolic products; measurement of oxidative metabolism in different parts of the DA nigrostriatal pathway; measurement of MAO activity in various animal species including MAO knock-out mice.

3,4-Dihydroxyphenylacetic Acid↗
PubMed2001

Time-dependent changes in adrenal cortex ultrastructure and corticosterone levels after noise exposure in male rats.

In response to a stressful stimulus, there is a marked activation of the hypothalamic-pituitary-adrenal axis leading to a release of adrenocorticotropic hormone. This, in turn, acts on the zona fasciculata of the adrenal cortex to increase corticosterone plasma levels. Given the frequency of chronic intermittent noise exposure in man, we selected loud noise to evaluate concomitant changes in the ultrastructure of the adrenal cortex and corticosterone release. Following chronic (21 days, 6 h per day) loud white noise exposure (100 dBA, 0-26 KHz), we found the zona fasciculata to be most sensitive to time-dependent ultrastructural changes. These consisted of modifications in cell compartments involved in hormone synthesis and release. On the other hand, we found a progressive increase in corticosterone plasma levels which reached a plateau 9 days after noise exposure. The significance of these changes, in relation to phenomena like sensitization to repetitive stress, are discussed. Furthermore, the present data suggest that chronic loud noise exposure might potentially lead to endocrine dysfunctions.

Adrenal Cortex↗
PubMed2000

Time-course and dose-response study on the effects of chronic L-DOPA administration on striatal dopamine levels and dopamine transporter following MPTP toxicity.

Despite a long-lasting therapeutic use of L-DOPA in Parkinson's disease, doubts still remain concerning the possibility that chronic L-DOPA might accelerate the progression of this movement disorder. To address this point, in the present study we examined the effects of chronic L-DOPA administration either in intact or MPTP-treated parkinsonian mice. We produced an intermediate striatal dopamine loss by administering a low dose of MPTP (30 mg/kg); then, we treated mice chronically, for different time intervals, with a daily dose of L-DOPA (50 mg/kg). In particular, to study the time-course of the effects of L-DOPA on the recovery of nigrostriatal dopamine axons, mice were sacrificed at 5, 30, 60, and 90 days after a daily L-DOPA administration. To evaluate presynaptic integrity of the nigrostriatal pathway we measured dopamine, metabolite levels, and dopamine uptake sites. In the same animals, we measured striatal serotonin levels and we analysed monoamine content in the olfactory bulb. Administration of MPTP produced a neurotoxic effect, which fully recovered in 2-3 months. Daily L-DOPA administration did not modify this recovery process. Additionally, there was no significant effect of L-DOPA in intact mice, despite a slight decrease in striatal dopamine levels at 5 and 30 days. However, this effect was neither worsened nor reproduced by administering higher doses of L-DOPA (up to 400 mg/kg) for the same amount of time. These data rule out neurotoxic effects induced by prolonged L-DOPA administration, both in intact and MPTP-treated mice. Moreover, administration of L-DOPA does not change the recovery process which takes place after a nigrostriatal lesion.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗
PubMed2000

Modulation of dihydroxyphenylacetaldehyde extracellular levels in vivo in the rat striatum after different kinds of pharmacological treatment.

We recently identified the direct product of dopamine (DA) by monoamine-oxidase (MAO) activity, dihydroxyphenylacetaldehyde (DOPALD) in the trans-striatal dialysate. Based on these findings, in this work, we directly measured the variations in DOPALD levels after various kinds of pharmacological treatment in rat striatal extracellular fluid. Using both reversible and irreversible MAO inhibitors, we found that MAO-A inhibition suppressed, whereas MAO-B inhibition did not modify DOPALD levels in the dialysate. The vesicular DA uptake blocker Ro 4-1284 led to an increase in extracellular DA and DOPALD, whereas the increase in extracellular DA obtained after administration of the plasma membrane DA uptake blocker GBR-12909 occurred without concomitant changes in DOPALD extracellular levels. Microinfusions of DA through the dialysis probe or systemic administration of L-DOPA increased striatal DOPALD to a greater extent compared with other DA metabolites, both in intact and in 6-hydroxydopamine (6-OHDA)-lesioned striatum. This study indicates that the direct product of MAO activity within the rat striatum derives from the activity of the isoenzyme MAO-A. The assay of DOPALD, together with DOPAC, represents a reliable tool to measure directly, in freely moving animals, DA oxidative metabolism. As recent studies have shown that microinfusions of exogenous DOPALD might induce cell death, pharmacological modulation of DOPALD levels might also be relevant for an understanding of the mechanisms involved in DA neurotoxicity.

3,4-Dihydroxyphenylacetic Acid↗
PubMed2000

The role of the locus coeruleus in the development of Parkinson's disease.

In Parkinson's disease, together with the classic loss of dopamine neurons of the substantia nigra pars compacta, neuropathological studies and biochemical findings documented the occurrence of a concomitant significant cell death in the locus coeruleus. This review analyzes the latest data obtained from experimental parkinsonism indicating that, the loss of norepinephrine in Parkinson's disease might worsen the dopamine nigrostriatal damage. Within this latter context, basic research provided a new provocative hypothesis on the significance of locus coeruleus in conditioning the natural history of Parkinson's disease. In particular, the loss of a trophic influence of these neurons might be crucial in increasing the sensitivity of nigrostriatal dopamine axons to various neurotoxic insults. In line with this, recently, it has been shown that locus coeruleus activity plays a pivotal role in the expression of various immediate early genes and in inducing the phosphorilation of cyclic adenosine monophosphate response element-binding proteins, suggesting a role of the nucleus in sustaining a protective effect.

Animals↗
PubMed2000

Similar increases in extracellular lactic acid in the limbic system during epileptic and/or olfactory stimulation.

Previous studies have shown that physiological stimulation of brain activity increases anaerobic glucose consumption, both in humans and in experimental animals. To investigate this phenomenon further, we measured extracellular lactate levels within different rat brain regions, using microdialysis. Experiments were performed comparing the effects of natural, physiological olfactory stimulation of the limbic system with experimental limbic seizures. Olfactory stimulation was carried out by using different odors (i.e. both conventional odors: 2-isobutyl-3-methoxypyrazine, green pepper essence; thymol; and 2-sec-butylthiazoline, a sexual pheromone). Limbic seizures were either induced by systemic injection of pilocarpine (200-400 mg/kg) or focally elicited by microinfusions of chemoconvulsants (bicuculline 118 pmol and cychlothiazide 1.2 nmol) within the anterior piriform cortex. Seizures induced by systemic pilocarpine tripled lactic acid within the hippocampus, whereas limbic seizures elicited by focal microinfusion of chemoconvulsants within the piriform cortex produced a less pronounced increase in extracellular lactic acid. Increases in extracellular lactate occurring during olfactory stimulation with the sexual pheromone (three times the baseline levels) were non-significantly different from those occurring after systemic pilocarpine. Increases in lactic acid following natural olfactory stimulation were abolished both by olfactory bulbectomy and by the focal microinfusion of tetrodotoxin, while they were significantly attenuated by the local application of the N-methyl-D-aspartate antagonist AP-5. Increases in hippocampal lactate induced by short-lasting stimuli (olfactory stimulation or microinfusion of subthreshold doses of chemoconvulsants, bicuculline 30 pmol) were reproducible after a short delay (1 h) and cumulated when applied sequentially. In contrast, limbic status epilepticus led to a long-lasting refractoriness to additional lactate-raising stimuli and there was no further increase in lactate levels when the olfactory stimulation was produced during status epilepticus. Increases in lactic acid following olfactory stimulation occurred with site specificity in the rhinencephalon (hippocampus, piriform and entorhinal cortex) but not in the dorsal striatum. Site specificity crucially relied on the quality of the stimulus. For instance, other natural stimuli (i.e. tail pinch) produced a similar increase in extracellular lactate in all brain areas under investigation. The major conclusion of this work is that the presentation of an odor known to be a rat pheromone results in lactate production as great as that induced by the systemic convulsant pylocarpine (maximum: 2.286+/-0.195 mM and 1.803+/-0.108 mM, respectively). This supports the notion that the great magnitude of lactate production known to accompany seizures can result from the intensified neural activity per se ("aerobic gycolysis"), not merely from local anoxia or other pathological changes.

2-Amino-5-phosphonovalerate↗