Francesco Orzi

Reinforcing and locomotor stimulant effects of cocaine are absent in mGluR5 null mutant mice

Both ionotropic and metabotropic glutamate receptors (mGluRs) are involved in the behavioral effects of pyschostimulants; however, the specific contributions of individual mGluR subtypes remain unknown. Here we show that mice lacking the mGluR5 gene do not self-administer cocaine, and show no increased locomotor activity following cocaine treatment, despite showing cocaine-induced increases in nucleus accumbens (NAcc) dopamine (DA) levels similar to wild-type (WT) mice. These results demonstrate a significant contribution of mGlu5 receptors to the behavioral effects of cocaine, and suggest that they may be involved in cocaine addiction.

Neuroprotection mediated by glial group-II metabotropic glutamate receptors requires the activation of the MAP kinase and the phosphatidylinositol-3-kinase pathways.

The mGlu2/3 receptor agonists 4‐carboxy‐3‐hydroxyphenylglycine (4C3HPG) and LY379268 attenuated NMDA toxicity in primary cultures containing both neurons and astrocytes. Neuroprotection was abrogated by PD98059 and LY294002, which inhibit the mitogen activated protein kinase (MAPK) and the phosphatidylinositol‐3‐kinase (PI‐3‐K) pathways, respectively. Cultured astrocytes lost the ability to produce transforming growth factor‐β1 (TGF‐β1) in response to mGlu2/3 receptor agonists when co‐incubated with PD98059 or LY294002. As a result, the glial medium was no longer protective against NMDA toxicity. Activation of the MAPK and PI‐3‐K pathways in cultured astrocytes treated with 4C3HPG or LY379268 was directly demonstrated by an increase in the phosphorylated forms of ERK‐1/2 and Akt. Similarly to that observed in the culture, intracerebral or systemic injections of mGlu2/3 receptor agonists enhanced TGF‐β1 formation in the rat or mouse caudate nucleus, and this effect was reduced by PD98059. PD98059 also reduced the ability of LY379268 to protect striatal neurons against NMDA toxicity. These results suggest that activation of glial mGlu2/3 receptors induces neuroprotection through the activation of the MAPK and PI‐3‐K pathways leading to the induction of TGF‐β.

Influence of Plasma Glucose Concentration on Lumped Constant of the Deoxyglucose Method: Effects of Hyperglycemia in the Rat

The lumped constant of the deoxyglucose method was determined by the steady-state, model-independent method in the brain of normal conscious rats with arterial plasma glucose concentrations varying from normoglycemia (i.e., 8 mM) to hyperglycemia (i.e., 31 mM). The lumped constant for brain was found to decrease very gradually with increasing arterial plasma glucose concentration from a value of ∼0.45 in the midnor-moglycemic range (i.e., 7–8 mM) to ∼0.38 at 28–31 mM. 3-O-[14C]Methylglucose was used to assess the distribution of glucose within the brain structures in hyperglycemia; the results indicated that the glucose concentration, and therefore also the values for the lumped constant, remain relatively uniform in hyperglycemia with arterial plasma glucose concentrations as high as 34 mM. The values for the lumped constant for rat brain determined in the present studies were combined with those previously determined in this laboratory for hypoglycemia and normoglycemia by the same method to provide a single source for the values for the lumped constant to be used over the full range of arterial plasma glucose concentrations. In several rats the lumped constant for cephalic extracerebral tissues was also evaluated in parallel with those for the brain. The lumped constant for the cephalic extracerebral tissues was found to be about twice that for brain and to be unaffected by changes in arterial plasma glucose levels.

Riluzole in patients with hereditary cerebellar ataxia: a randomised, double-blind, placebo-controlled trial

BACKGROUND Our previous study in patients with cerebellar ataxias of different causes showed significant benefit of riluzole after 8 weeks. We aimed to confirm these results in patients with spinocerebellar ataxia or Friedreichs ataxia in a 1-year trial. METHODS Patients with spinocerebellar ataxia or Friedreichs ataxia (2:1 ratio) from three Italian neurogenetic units were enrolled in this multicentre, double-blind, placebo-controlled trial, and randomly assigned to riluzole (50 mg orally, twice daily) or placebo for 12 months. The randomisation list was computer-generated and a centralised randomisation system was implemented. Participants and assessing neurologists were masked to treatment allocation. The primary endpoint was the proportion of patients with improved Scale for the Assessment and Rating of Ataxia (SARA) score (a drop of at least one point) at 12 months. An intention-to-treat analysis was done. This trial is registered at ClinicalTrials.gov, number NCT01104649. FINDINGS Between May 22, 2010, and Feb 25, 2013, 60 patients were enrolled. Two patients in the riluzole group and three in the placebo group withdrew their consent before receiving treatment, so the intention-to-treat analysis was done on 55 patients (19 with spinocerebellar ataxia and nine with Friedreichs ataxia in the riluzole group, and 19 with spinocerebellar ataxia and eight with Friedreichs ataxia in the placebo group). The proportion with decreased SARA score was 14 (50%) of 28 patients in the riluzole group versus three (11%) of 27 in the placebo group (OR 8·00, 95% CI 1·95-32·83; p=0·002). No severe adverse events were recorded. In the riluzole group, two patients had an increase in liver enzymes (less than two times above normal limits). In two participants in the riluzole group and two participants in the placebo group, sporadic mild adverse events were reported. INTERPRETATION Our findings lend support to the idea that riluzole could be a treatment for cerebellar ataxia. Longer studies and disease-specific trials are needed to confirm whether these findings can be applied in clinical practice. FUNDING Agenzia Italiana del Farmaco.

Local cerebral glucose utilization following unilateral and bilateral lesions of the nucleus basalis magnocellularis in the rat

To investigate to what extent the loss of cholinergic projections to the neocortex results in functional impairment in the target areas, local rates of cerebral glucose utilization were measured following excitotoxin lesions of the nucleus basalis magnocellularis (NBM) in the rat. Both unilateral and bilateral lesions of NBM resulted in reversible depression of cerebral metabolism. The effects of unilateral lesions were limited to the cortical areas which receive most of the cholinergic projections from NBM. The metabolic defect produced by bilateral lesions was spread to the whole brain. Within 4 months, however, normal metabolic values coexisted with marked changes of the presynaptic cholinergic markers and impairment of conditioned behavior.

White matter microstructural alterations in migraine: A diffusion-weighted MRI study

Summary White matter disintegration, as measured by diffusion‐weighted MRI, is reported in migraineurs, and is speculated to be either a marker of possible white matter disintegration or maladaptive plasticity. Abstract Migraine is a common and disabling neurological disease. The pathomechanism that underlies the disorder is not entirely understood, and reliable biomarkers are missing. In the current analysis we looked for microstructural alterations of the brain white matter in migraine patients by means of diffusion‐weighted magnetic resonance imaging. The measurements were carried out with a novel approach based on fine‐tuned nonlinear registration and nonparametric permutation test in an alignment‐invariant tract representation (Tract‐Based Spatial Statistics). We found reduced fractional anisotropy in the right frontal white matter cluster of migraine patients. In the same region we also found increased mean diffusivity and increased radial diffusivity. The probabilistic tractography showed connection of this cluster to other parts of the pain network (orbitofrontal cortex, insula, thalamus, dorsal midbrain). We speculate that these findings reflect maladaptive plastic changes or white matter disintegration.

REPEATED ELECTROCONVULSIVE SHOCK INCREASES GLIAL FIBRILLARY ACIDIC PROTEIN, ORNITHINE DECARBOXYLASE, SOMATOSTATIN AND CHOLECYSTOKININ IMMUNOREACTIVITIES IN THE HIPPOCAMPAL-FORMATION OF THE RAT

Rats were submitted to single or repeated (7 days, one session for each day) sessions of electroconvulsive shock. A computer-assisted morphometric and microdensitometric analysis of glial fibrillary acidic protein-, ornithine decarboxylase-, somatostatin- and cholecystokinin-like immunoreactivities was performed in the hippocampal formation and other brain areas. The results of the study showed a significant increase of the intensity of the immunostaining for glial fibrillary acidic protein, ornithine decarboxylase, somatostatin and cholecystokinin in the hippocampal formation and distinctively in the dentate gyrus following repeated, but not single, electroconvulsive shock. No significant change was found in the number of somatostatin- and cholecystokinin-like immunoreactive cell bodies in any hippocampal subregion and in the number of glial cells in the hilus of dentate gyrus in rats treated with single or repeated electroconvulsive shock. It is a distinct possibility that the observed increase in the content of the neuropeptides in the hippocampal formation reflects a compensatory response of the brain to seizure-inducing stimuli and that such an increase may play a role in the therapeutic effect of electroconvulsive shock.

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 Parkinsons 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 Parkinsons disease.

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 Parkinsons 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.

Disease Outcome, Alexithymia and Depression are Differently Associated with Serum IL-18 Levels in Acute Stroke

Stroke has been shown to lead to depressive disorders, anxiety disorders and other emotional consequences. Although the cause of these disorders is a subject of debate, stroke has clearly been shown to lead to the production of pro-inflammatory cytokines, which we hypothesized to play a role in the production of post-stroke emotional disorders. Thus we investigated here whether acute stroke might be associated with changes in the normal serum levels of IL-18 and if these changes were related to stroke severity, as well as to the presence and severity of alexithymia and depression. Thirty patients with a first-ever symptomatic ischemic stroke were included. Alexithymia (Toronto Alexithymia Scale; TAS-20), depression (Hamilton Depression Rating Scale; HDRS-17) and serum IL-18 were assessed. Stroke patients showed serum levels of IL-18 significantly related to stroke severity. Furthermore, a strong positive correlation was observed between IL-18 levels and severity of alexithymia, particularly among patients with right-hemisphere lesions. Specifically, circulating concentrations of IL-18 were significantly increased in patients with categorical alexithymia (TAS-20 score 61), as compared with both non alexithymic patients and control subjects. In addition, stroke was more severe in alexithymic patients, as compared to non alexithymic patients. Following multivariate regression, serum IL-18 levels appeared to be specifically associated with alexithymia rather than with stroke severity in patients with right-hemisphere lesions only. These results suggest that IL-18 might be specifically implicated in the pathogenesis of post-stroke alexithymia, ultimately contributing to impaired recovery from stroke.