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P Spano

Publications and source records attributed to P Spano.

At least 19 recordsLinked to original sources
PubMed2006

Selective disarrangement of the rostral telencephalic cholinergic system in heterozygous reeler mice.

Reelin (RELN) is a key molecule for the regulation of neuronal migration in the developing CNS. The reeler mice, which have spontaneous autosomal recessive mutation in the RELN gene, reveal multiple defects in brain development. Morphological, neurochemical and behavioral alterations have been detected in heterozygous reeler (HR) mice, suggesting that not only the presence, but also the level of RELN influences brain development. Several studies implicate an involvement of RELN in the pathophysiology of neuropsychiatric disorders in which an alteration of the cholinergic cortical pathways is implicated as well. Thus, we decided to investigate whether the basal forebrain (BF) cholinergic system is altered in HR mice by examining cholinergic markers at the level of both cell body and nerve terminals. In septal and rostral, but not caudal, basal forebrain region, HR mice exhibited a significant reduction in the number of choline acetyltransferase (ChAT) immunoreactive (ir) cell bodies compared with control mice. Instead, an increase in ChAT ir neurons was detected in lateral striatum. This suggests that an alteration in ChAT ir cell migration which leads to a redistribution of cholinergic neurons in subcortical forebrain regions occurs in HR mice. The reduction of ChAT ir neurons in the BF was paralleled by an alteration of cortical cholinergic nerve terminals. In particular, the HR mice presented a marked reduction of acetylcholinesterase (AChE) staining accompanied by a small reduction of cortical thickness in the rostral dorsomedial cortex, while the density of AChE staining was not altered in the lateral and ventral cortices. Present results show that the cholinergic basalo-cortical system is markedly, though selectively, impaired in HR mice. Rostral sub-regions of the BF and rostro-medial cortical areas show significant decreases of cholinergic neurons and innervation, respectively.

Acetylcholine↗
PubMed2001

Alternative splicing of mGlu6 gene generates a truncated glutamate receptor in rat retina.

A novel splice variant of metabotropic glutamate receptor type 6 (mGlu6 receptor) was identified by reverse transcription-polymerase chain reaction amplification and sequence analysis of rat retina cDNA. The new rat receptor isoform (mGlu6b receptor) is characterized by an additional exon of 88 nucleotides containing an inframe stop codon, thus predicting the expression of a truncated protein of 508 amino acids. In situ hybridization reveals mGlu6b receptor mRNA to be predominantly expressed in the outer part of the inner nuclear layer of rat retina, containing ON-bipolar cells. The mGlu6b protein would comprise the extracellular domain of the receptor containing the ligand-binding site, but would lack the transmembrane and intracellular portions, thus possibly acting as a retinal soluble receptor for glutamate.

Alternative Splicing↗
PubMed2001

Identification of novel alternatively-spliced mRNA isoforms of metabotropic glutamate receptor 6 gene in rat and human retina.

Novel splice variants of metabotropic glutamate receptor type 6 (mGlu6 receptor) were identified by reverse transcription-polymerase chain reaction (RT-PCR) amplification and sequence analysis of rat and human retina cDNAs. The new rat mGlu6 receptor mRNA isoform is characterized by an additional exon of 88 nucleotides containing an in frame stop codon, thus predicting the expression of a truncated protein of 508 amino acids. The human retina was found to express two different mGlu6 receptor mRNA variants: one lacking 97 nucleotides from exon 6, the other including five nucleotides of intron 5. These mRNAs would encode truncated receptors of 425 and 405 amino acids, respectively. Both in rats and in humans, the truncated mGlu6 receptor proteins would comprise the extracellular domain but lack the transmembrane and intracellular portion of the receptor, thus possibly acting as retinal soluble receptors for glutamate. Though generated by different patterns of alternative splicing, the inter-species conservation of truncated mGlu receptor molecules strongly suggest their relevance in the regulatory network of glutamatergic neurotransmission.

Alternative Splicing↗
PubMed2001

Selective immunolesioning of cholinergic neurons in nucleus basalis magnocellularis impairs prepulse inhibition of acoustic startle.

Information processing and attentional abnormalities are prominent in neuropsychiatric disorders. Since the cholinergic neurons located in the nucleus basalis magnocellularis have been shown to be involved in attentional performance and information processing, recent efforts to analyze the significance of the basal forebrain in the context of schizophrenia have focused on this nucleus and its projections to the cerebral cortex. We report here that bilateral selective immunolesioning of the cholinergic neurons in the nucleus basalis magnocellularis is followed by significant deficits in sensorimotor gating measured by prepulse inhibition of the startle reflex in adult rats. This behavioral approach is used in both humans and rodents and has been proposed as a valuable model contributing to the understanding of the neurobiological substrates of schizophrenia. The disruption of prepulse inhibition persisted over repeated testing. The selective lesions were induced by bilateral intraparenchymal infusions of 192 IgG saporin at a concentration having minimal diffusion into adjacent nuclei of the basal forebrain. The infusions were followed by extensive loss of choline acetyltransferase-immunopositive neurons. Our results show that the cholinergic neurons of the nucleus basalis magnocellularis represent a critical station of the startle gating circuitry and suggest that dysfunction of these neurons may result in impaired sensorimotor gating characteristic of schizophrenia.

Acetylcholine↗
PubMed2000

Efficacy of rivastigmine in dementia with Lewy bodies: a randomised, double-blind, placebo-controlled international study.

BACKGROUND: Dementia with Lewy bodies is a common form of dementia in the elderly, characterised clinically by fluctuating cognitive impairment, attention deficits, visual hallucinations, parkinsonism, and other neuropsychiatric features. Neuroleptic medication can provoke severe sensitivity reactions in patients with dementia of this type. Many deficits in cholinergic neurotransmission are seen in the brain of patients with Lewy-body dementia; therefore, drugs enhancing central cholinergic function represent a rationally-based therapeutic approach to this disorder. Rivastigmine, a cholinesterase inhibitor, was tested in a group of clinically characterised patients with Lewy-body dementia. METHODS: A placebo-controlled, double-blind, multicentre study was done in 120 patients with Lewy-body dementia from the UK, Spain, and Italy. Individuals were given up to 12 mg rivastigmine daily or placebo for 20 weeks, followed by 3 weeks rest. Assessment by means of the neuropsychiatric inventory was made at baseline, and again at weeks 12, 20, and 23. A computerised cognitive assessment system and neuropsychological tests were also used, and patients underwent close medical and laboratory safety analysis. FINDINGS: Patients taking rivastigmine were significantly less apathetic and anxious, and had fewer delusions and hallucinations while on treatment than controls. Almost twice as many patients on rivastigmine (37, 63%), than on placebo (18, 30%), showed at least a 30% improvement from baseline. In the computerised cognitive assessment system and the neuropsychological tests, patients were significantly faster and better than those on placebo, particularly on tasks with a substantial attentional component. Both predefined primary efficacy measures differed significantly between rivastigmine and placebo. After drug discontinuation differences between rivastigmine and placebo tended to disappear. Known adverse events of cholinesterase inhibitors (nausea, vomiting, anorexia) were seen more frequently with rivastigmine than with placebo, but safety and tolerability of the drug in these mostly multimorbid patients were judged acceptable. INTERPRETATION: Rivastigmine 6-12 mg daily produces statistically and clinically significant behavioural effects in patients with Lewy-body dementia, and seems safe and well tolerated if titrated individually.

Aged↗
PubMed2000

Differential gene expression of dopamine D-2 receptor subtypes in rat chromaffin cells and sympathetic neurons in culture.

Chromaffin cells and sympathetic neurons arise from a common bipotential progenitor which, if exposed to nerve growth factor (NGF), matures into a sympathetic neuron, but if exposed to glucocorticoids (GCs), differentiates into a mature chromaffin cell. Pharmacological evidence indicates that, in adrenal medulla and sympathetic neurons, dopamine (DA) receptors belonging to the D-2 family inhibit catecholamine secretion. The molecular characterization of these receptors, however, is not been yet described. Our data suggest that bipotential cells obtained from newborn rat adrenal medulla express both isoforms of the D-2 receptor, while D-3 receptor and D-4 receptor messenger RNAs (mRNAs) are not present. GC-mediated maturation induces the expression of D-4 receptors, without modification of D-2 isoforms. Sympathetic neurons differentiated in vitro selectively express the D-2short mRNA. Taken together, present results suggest that NGF and GCs play a role in regulating D-2 family receptor expression in neural crest-derived cells.

Animals↗
PubMed2000

From the mind to the brain: an unusual pathway.

One of the most unrecognized aspects of Golgi's life was his deep interest in neuropsychiatry. From 1865 to 1868 he attended the Clinica per le Malattie Nervose e Mentali in Pavia directed by Cesare Lombroso, the founder of modern criminology. Golgi was involved in research on the etiology of psychiatric ailments. During this short period of time he produced significant theoretic advances in clinical psychiatry. However, very soon he started to criticize the conceptual approach as well as the nosological system proposed by his academic mentor. In July 1868 he left Lombroso's school in search for a more rational method of studying brain functions and diseases. In spite of his anatomical approach to the central nervous system, he always maintained curiosity in the phenomenology of functional and organic mental disorders. This predisposition is witnessed by his capability to relate clinical observations to neuropathological findings.

Behavioral Symptoms↗
PubMed1999

Neuroprotective effect of thyrotropin-releasing hormone against excitatory amino acid-induced cell death in hippocampal slices.

Thyrotropin-releasing hormone (TRH) and some of its stable analogues have recently been shown to improve functional recovery after neurologic dysfunctions, such as brain trauma and epilepsy, in both animals and humans. The exact mechanism by which TRH produces its neuroprotective effects is still uncertain. The present study provides the first evidence that TRH exerts a neuroprotective effect against N-methyl-D-aspartate (NMDA)-mediated excitotoxicity in rat hippocampal slices. TRH concentration dependently reduced NMDA toxicity by a mechanism that was highly sensitive to the protein kinase C blocker, bisindolilmaleimide. Delayed application of TRH, during NMDA exposure, still produced neuroprotection.

Animals↗
PubMed1999

Distribution and kainate-mediated induction of the DNA mismatch repair protein MSH2 in rat brain.

DNA repair is one of the most essential systems for maintaining the inherited nucleotide sequence of genomic DNA over time. Repair of DNA damage would be particularly important in neurons, because these cells are among the longest-living cells in the body. MSH2 is one of the proteins which are involved in the recognition and repair of a specific type of DNA damage that is characterized by pair mismatches. We studied the distribution of MSH2 in rat brain by immunohistochemical analysis. We found the level of MSH2 expression in rat brain to be clearly heterogeneous. The highest intensity of staining was found in the pyramidal neurons of the hippocampus and in the entorhinal and frontoparietal cortices. Positive cells were observed in the substantia nigra pars compacta, in cerebellar granular and Purkinje cells, and in the motor neurons of the spinal cord. We investigated the possible modulation of MSH2 expression after injection of kainate. Systemic administration of kainate induces various behavioural alterations and a typical pattern of neuropathology, with cell death in the hippocampal pyramidal neurons of the CA3/CA4 fields. Kainate injection also resulted in a marked, dose-dependent increase of MSH2 immunoreactivity in the hippocampal neurons of the CA3/CA4 fields. The effect was specific, since no changes in immunoreactivity were detected in the dentate gyrus nor in other brain areas. In summary, our data suggest that a mismatch DNA repair system, of which MSH2 protein is a representative component, is heterogeneously expressed in the rat brain and specifically induced by an experimental paradigm of excitotoxicity.

Animals↗
PubMed1999

Growth factors in pituitary tumors.

Prolactin-secreting tumors are the most frequently occurring neoplasms in the human pituitary. Although the clinical syndrome associated with prolactinomas is well recognized the molecular and cellular mechanisms leading to cell transformation and development of these tumors remain elusive. In this paper we summarize recent evidence suggesting that both hypothalamic and intrapituitary defects can be involved in the development of prolactinomas. In particular alterations of the hypothalamo-pituitary dopaminergic transmission result in the dysregulation of the proliferative activity of lactotrope cells leading to tumor development. Similarly changes in the expression and activity of resident growth factors also play a role in pituitary tumorigenesis. In particular both overexpression of TGF alpha and loss of NGF production appear to be involved in the development and progression of prolactin-secreting tumors.

Adenoma↗
PubMed1999

Reversal of glutamate excitotoxicity by activation of PKC-associated metabotropic glutamate receptors in cerebellar granule cells relies on NR2C subunit expression.

Stimulation of metabotropic glutamate receptors (mGluRs) belonging to group I has been found to reduce N-methyl-D-aspartate (NMDA) receptor function in terms of both intracellular calcium concentration ([Ca2+]i) rise and neurotoxicity in cultured cerebellar granule cells. In the present study, we investigated whether the mGluR-elicited modulation of glutamate responses might rely on the heteromeric composition of NMDA receptor channel. NMDA receptors consist of two distinct groups of subunits: NR1, that is ubiquitously in the receptor complexes; and NR2A-D, that differentiate and potentiate NMDA receptor responses by assembling with NR1. Among NR2 subunits, only NR2A and NR2C mRNAs and relative proteins are detected in cerebellar granule cells at 10 days in vitro. To dissect the involvement of the two different subunits in making the NMDA receptor channel sensitive to modulation by group I mGluR agonists, expression of the NR2C subunit was prevented by treating the cells with specific antisense oligodeoxynucleotide (ODN). The capability of the mGluR agonists, trans-1-amino-cyclopentane-1,3-dicarboxylic acid (tACPD, 100 microM) or 3 hydroxyphenylglycine (3HPG, 100 microM), and the protein kinase C (PKC) activator, 4beta-phorbol-12,13-dibutyrate (PDBu, 1 microM), to inhibit the function of resultant NMDA receptors was then evaluated. We found that depletion of the NR2C subunit abolished the inhibitory effect of group I mGluR stimulation on glutamate-induced [Ca2+]i rise and neurotoxicity. The antisense ODN treatment also prevented the inhibitory effect of PDBu on glutamate responses. Conversely, in NR2C-lacking neurons, both group I mGluRs and PKC stimulation enhanced NMDA receptor-mediated effects. The present findings indicate that the capability of PKC-associated mGluRs to modulate native NMDA receptor function relies on the heteromeric configuration of the receptor-channel complex. Particularly, expression of the NR2C subunit is required to make the NMDA receptor sensitive to inhibitory modulation by mGluRs or PKC activation.

Animals↗
PubMed1999

Suppression of telomerase, reexpression of KAI1, and abrogation of tumorigenicity by nerve growth factor in prostate cancer cell lines.

Nerve growth factor (NGF) is expressed in the prostate, where it appears to be involved in the control of epithelial cell growth and differentiation. NGF production is decreased in prostate tumors. However, the role of this neurotrophin in the control of proliferation and progression of prostate cancers is still a matter of investigation. Prostate adenocarcinomas are telomerase-positive tumors. Chronic exposure of DU145 and PC3 prostate tumor cell lines to NGF resulted in a dramatic down-regulation of telomerase activity. This effect was correlated in terms of concentrations and time with a remarkable down-regulation of cell proliferation both in vitro and in vivo but was not secondary to NGF-induced quiescence. No down-regulation of telomerase activity was, in fact, detectable during serum starvation-induced quiescence. LNCaP cells, which do not express NGF receptors, appear to be insensitive to the actions of NGF. DU145 and PC3 cells do not express the KAI1 metastasis suppressor gene, which is present in the prostate and is progressively lost during the progression of prostate cancers. Chronic NGF treatment strongly induced the reexpression of this gene in these cell lines, and this effect was correlated with the suppression of their invasive potential in vitro. The data presented here suggest that NGF reverts two metastatic prostate cancer cell lines to slowly proliferating, noninvasive phenotypes characterized by a very low telomerase activity and by the expression of the KAI1 metastasis suppressor gene.

Adenocarcinoma↗
PubMed1998

Nerve growth factor in pituitary development and pituitary tumors.

Cells in the anterior pituitary originate from a common pluripotent precursor whose phenotypic development is determined by intrapituitary transcription factors as well as by hypothalamic and peripheral signals. A rapidly growing body of evidence revealed that essential to the differentiation and proliferation of pituitary cells are an array of growth factors that are produced within the pituitary and act mainly through autocrine mechanisms. Growth factors are polypeptides that are released in carefully measured amounts by some cells to regulate cell growth and differentiation by activating specific tyrosine kinase receptors in the plasma membrane of target cells. Both overproduction of mitogenic growth factors and loss of factors inhibiting cell proliferation result in uncontrolled cell growth and tumor development. There is now increasing evidence that disruption of the calibrated signalling network activated by pituitary growth factors plays a central role in pituitary tumorigenesis. This paper is focussed on the role of nerve growth factor (NGF) in pituitary physiology and pathology. In particular, we propose that NGF plays a dual role in the gland: a local one as a stimulator of differentiation and proliferation of lactotrope cells during pituitary development and a systemic one as a neurohormone which is cosecreted with prolactin into the bloodstream. Furthermore, we discuss the evidence that NGF is an autocrine differentiation factor for prolactin-secreting cells. Escape from NGF control appears to be one of the mechanisms involved in the development and progression of prolactinomas. Along the same line, exposure of prolactinomas refractory to dopaminergic therapy to exogenous NGF results in their differentiation into lactotrope-like cells reexpressing the D2 receptor protein. This observation may open the way to a sequential therapy with NGF and bromocriptine for patients refractory to the conventional therapy.

Animals↗
PubMed1998

Induction of tumour-suppressor phosphoprotein p53 in the apoptosis of cultured rat cerebellar neurones triggered by excitatory amino acids.

We found that primary cultures of rat cerebellar granule cells, although definitely postmitotic and terminally differentiated, express the tumour-suppressor phosphoprotein p53. In particular, granule cells both expressed significant levels of p53 mRNA and positively reacted to an anti-p53 antibody, from the first day of culturing. During neurone differentiation, p53 mRNA content did not significantly change, at least up to 12 days in vitro, while p53 immunoreactivity increased gradually. p53 expression appeared to be further modulable being upregulated after stimulation of glutamate ionotropic receptors by glutamate or kainate. Although qualitatively similar, p53 induction by glutamate and kainate differed in terms of intensity and time-course. The glutamate increase of p53 immunoreactivity appeared within 30 min after the treatment and lasted for at least 2 h. Kainate-induced increase of p53 immunoreactivity was delayed, becoming apparent within 2 h and lasting for at least 8 h. Both kainate- and glutamate-induced increases of p53 immunoreactivity were prevented by the non-competitive NMDA receptor antagonist MK 801. As shown by the electrophoretic mobility shift analysis, both glutamate and kainate induced increases of p53 DNA binding activity. Blockade of p53 induction by a specific p53 antisense oligonucleotide resulted in a partial reduction of excitotoxicity with a complete inhibition of the excitatory amino acids induced apoptosis. Our data suggest that stimulation of ionotropic glutamate receptors in neurones results in a p53-dependent apoptosis.

Animals↗
PubMed1997

Opposite effects of dopamine D2 and D3 receptors on learning and memory in the rat.

Mesolimbocortical dopamine plays a role in learning and memory. The specific receptor subtypes mediating the effects of dopamine, however, are still unknown. Dopamine D2, D3 and D4 receptors are expressed in the hippocampus and dopamine D3 receptors are present in the septal area, suggesting that these receptor subtypes can contribute to the behavioral effects of dopamine D2-like receptor agonists. We now investigated the role of dopamine D2 and D3 receptors in learning and memory by using the transient amnesia induced by scopolamine in the passive avoidance test as experimental model. The data strongly suggest that both dopamine D2 and D3 receptors mediate the effects of dopamine on the integrative function of learning and memory. In particular, we show that the non-selective dopamine agonist apomorphine prevents the scopolamine-induced disruption of consolidation of the previously acquired passive avoidance behavior. This effect is mediated by receptors belonging to the dopamine D2 family since it was antagonized by (-)-sulpiride and mimicked by quinpirole. Nafadotride, a relatively selective antagonist for dopamine D3 receptors, antagonized scopolamine-induced memory disruption and potentiated the facilitatory effect of quinpirole. Taken together, these results suggest that the effects of dopamine on memory consolidation are the result of a balance between dopamine D2 receptor-mediated facilitation and dopamine D3 receptor-mediated inhibition, and that dopamine D2 and D3 receptors play opposite roles in the control of the mechanisms leading to memory consolidation.

Amnesia↗
PubMed1997

Metabotropic glutamate receptor mRNA expression in rat spinal cord.

It has recently become clear that, analogous to the situation observed in the brain, glutamatergic neurotransmission in the spinal cord relies upon the activation of ionotropic and metabotropic glutamate receptors (mGluRs). Although electrophysiological studies have emphasized the relevance of mGluR activation in the modulation of spinal neuron responses to glutamate, a detailed study of the molecular forms of receptors belonging to the mGluR family in the spinal cord is still lacking. Using a reverse transcriptase-polymerase chain reaction technique with primers specifically recognizing each cloned mGluR subtype, we found that rat adult spinal cord specifically expresses high levels of mRNA encoding mGluR1a but not mGluR1b. The expression of mRNAs for mGluRs 5a and 5b was also found at levels roughly comparable to that observed in mGluR5-positive brain areas. mGluR2, mGluR3, mGluR4 and mGluR7 mRNAs appeared to be expressed at lower levels, while mGluR6 and mGluR8 mRNAs were not detectable.

Animals↗