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A Contestabile

Publications and source records attributed to A Contestabile.

At least 55 records · Page 3Linked to original sources
PubMed1994

Impaired neurogenesis by methylazoxymethanol in newborn rats results in transient reduction of ornithine decarboxylase and polyamines in the cerebellum, but not in the olfactory bulbs.

Polyamines and the key enzyme for their biosynthesis, ornithine decarboxylase (ODC) play an important role in the control of neuronal proliferation and differentiation. Exposure to agents that interfere with normal cell maturation is expected to result in alteration of neuronal ODC developmental pattern. We have administered to newborn rats, about 6 and 30 hr after birth, 20 mg/kg of methylazoxymethanol acetate (MAM), an agent able to selectively kill dividing cells and we have evaluated ODC activity and polyamine levels in the cerebellum and ODC activity in the olfactory bulbs at various developmental stages starting from postnatal day 4 (PD 4) until PD 28. Cerebellar weight decreased by 22-50% at the different developmental stages in MAM-treated animals. A decline in ODC specific activity was observed at PD 4 and a decrease of putrescine levels at PD 4 and PD 6 in the cerebellum. At PD 10, however, both ODC activity and putrescine level were increased in MAM-treated animals. Spermidine levels were never affected by the treatment, while spermine was significantly decreased at PD 6 and PD 8. These results demonstrate that altered ontogenetic patterns of ODC activity and polyamine levels are the consequence of disturbance of the normal process of brain maturation. No significant differences in specific ODC activity were noticed in the olfactory bulbs of MAM-treated rats. This may be related to the more widespread time-span of neurogenesis in this region, a fact that is also revealed by the higher ODC activity constitutively expressed at times in which neurogenesis has ended in the rest of the brain.

Aging↗
PubMed1993

Structural, neurochemical and behavioural consequences of neonatal blockade of NMDA receptor through chronic treatment with CGP 39551 or MK-801.

Recent evidence suggests that NMDA receptors may be involved in survival of neurons and establishment of correct connectivity during development. We have treated rat pups from postnatal day 1 to 22 with daily s.c. injections of a competitive (CGP 39551) and a non-competitive (MK-801) antagonist of the NMDA receptor. Body weight of treated rats was decreased by 50-65% at postnatal day 24 and by 25-32% at 70 days of age. Brain weight was decreased by 16-24% at both ages. Among the different brain regions, the cerebellum and striatum appeared more decreased in size than the cortex and hippocampus. Only few minor, and in some cases transient, differences were measured in the cerebellum, the hippocampus and the cortex for a battery of neurochemical markers related to cholinergic, GABAergic and glutamatergic transmission as well as to astrocyte and oligodendrocyte activity. When tested in actometric cages from postnatal days 28 to 60, treated rats exhibited a dramatic increase of spontaneous locomotor activity which was maximal in 28-day-old animals (380% and 250% of control values in CGP 39551 and MK-801 groups, respectively) and was still significant at 60 days of age. Therefore, long-lasting alteration of motor behaviour is obtained by the schedule of chronic treatment adopted for the present experiments. Our results suggest that blockade of NMDA receptors during the critical period of brain maturation may result in permanent alteration of neural circuits.

2-Amino-5-phosphonovalerate↗
PubMed1993

Ornithine decarboxylase is differentially induced by kainic acid during brain development in the rat.

The induction of brain ornithine decarboxylase (ODC) as a consequence of systemic kainic acid administration was studied in the hippocampus and the olfactory cortex-amygdala area of 10-day-old rat pups and 30-day-old young rats. In pups, ODC levels were moderately increased (plus 50-80%) 4 h after kainic acid administration, coming back quickly to control levels afterwards. In young rats, instead, ODC levels were dramatically increased by 17-25-fold, 16 h after kainic acid administration and decreased towards basal levels 48-72 h after injection. The present results suggest that the process of excitotoxic ODC induction can be split in two phases: a first phase characterized by moderate induction and essentially linked to the overstimulation of brain circuits and a second phase, during which a dramatic enzyme stimulation is accompanied by the appearance of neurodegenerative pathology.

Amygdala↗
PubMed1993

Pharmacokinetics of antifungal agents.

The authors have evaluated the pharmacokinetics of four antifungal agents used in the therapy of fungal peritonitis. Amphotericin B (Amph B) poorly diffuses from blood into peritoneal fluid, which intraperitoneal administration induces severe abdominal pain. 5-Fluorocytosine (5FC) easily crosses peritoneum, but resistance may appear when the drug is used alone. Ketoconazole (K) poorly penetrates into peritoneal fluid, while Fluconazole (F), used per os or intraperitoneally, shows a good antifungal activity both in serum and in the peritoneal fluid. In conclusion, from a pharmacokinetic point of view, all the antifungal agents examined, perhaps with the exception of F, do not offer, when used alone, sufficient guarantees in curing peritonitis. Therefore, for treating fungal infections in CAPD, drug combinations such as AmphB + 5FC, K + 5FC or 5FC+F have to be used.

Amphotericin B↗
PubMed1992

Melittin enhances excitatory amino acid release and AMPA-stimulated 45Ca2+ influx in cultured neurons.

Melittin, a potent activator of phospholipase A2, enhanced both spontaneous and depolarization-induced release of D-[3H]aspartate in primary cultures of cerebellar granule cells. The action of melittin was concentration-dependent (EC50 value = 300 ng/ml) and did not require the presence of extracellular Ca2+. Melittin also stimulated the release of glutamate and aspartate, in addition to other endogenous amino acids (taurine, alanine and gamma-aminobutyric acid). These effects were accompanied by an enhanced influx of 45Ca2+, which was in part mediated by the activation of excitatory amino acid receptors by endogenous agonists. Low concentrations of melittin (50 ng/ml) potentiated the efficacy of AMPA in stimulating 45Ca2+ influx without affecting stimulation by kainate or by glutamate added in the absence of extracellular Mg2+ (a condition that favors the activation of NMDA receptors). These results indicate that activation of phospholipase A2 evokes both an enhanced glutamate release and an increased sensitivity of AMPA receptors, two events that may support synaptic facilitation and LTP formation.

Amino Acids↗
PubMed1992

Antagonists of the NMDA receptor and allopurinol protect the olfactory cortex but not the striatum after intra-cerebral injection of kainic acid.

Overstimulation of the NMDA receptor, as well as generation of excessive amounts of free radicals, has been implicated in excitotoxic brain injuries. We report here that two antagonists of the NMDA receptor and an inhibitor of the free radical-generating enzyme, xanthine oxidase, protect the olfactory cortex but not the striatum after intrastriatal injection of kainic acid. Our results suggest the existence of a precise link between excitotoxic activation of the NMDA receptor and neuropathology related to excessive amounts of free radicals. The focal point of this link may be the entry of Ca2+ through the NMDA receptor and the consequent activation of proteases and free radical-generating systems.

Allopurinol↗
PubMed1992

Induction of brain ornithine decarboxylase after systemic or intrastriatal administration of kainic acid.

The activity of ornithine decarboxylase (ODC), the key enzyme of polyamine biosynthesis, dramatically increases after different types of brain injuries. The role of this induction is still unclear. We report here data on the temporal pattern of ODC induction caused by the excitotoxin kainic acid. After systemic administration, ODC activity increases severalfold peaking at 8 h in the prefrontal cortex and at 16 h in the olfactory cortex and hippocampus. After intrastriatal injection, the peak of induction is reached at 32 h, while a smaller and more transient increase is also observed in the contralateral, saline-injected striatum. We suggest that ODC induction is initially linked to overactivation of neural circuits and, later on, to the development of widespread neural damage.

Animals↗
PubMed1992

Immunohistochemistry and neurochemistry of the habenulo-interpeduncular connection after partial developmental depletion of habenular cholinergic neurons in the rat.

The habenulo-interpeduncular system of the rat constitutes an interesting model to address quantitatively problems related to synaptogenesis and to the interactions between neuronal populations after selective alteration of these elements during development. In the present study this has been achieved by experimentally reducing, through gestational treatment with methylazoxymethanol acetate (MAM), the population of cholinergic neurons of the medial habenula which projects to the interpeduncular nucleus. Immunohistochemical analysis gave evidence that the topographical localization of the cholinergic and the substance P-containing populations in the medial habenula was not altered by MAM treatment. Furthermore, the topographical distribution of cholinergic fibers and terminals in the interpeduncular nucleus, which reflects the habenulo-interpeduncular projection as well as cholinergic projections coming from different sources, was substantially preserved. The same was also true concerning the terminal distribution of substance P in the interpeduncular nucleus. Quantitative radioassays demonstrated a sizable decrease of overall ChAT activity in both the habenulae and the interpeduncular nucleus. By comparison of 1 month-old and 3 month-old animals it appeared that this effect was partially reversed with age in the interpeduncular nucleus.

Animals↗
PubMed1992

Protection from kainic acid neuropathological syndrome by NMDA receptor antagonists: effect of MK-801 and CGP 39551 on neurotransmitter and glial markers.

Systemic administration of kainic acid results in the development of a characteristic convulsive syndrome, accompanied by neuropathological alterations and loss of transmitter markers in some forebrain regions. Since some of these effects appear to involve the N-methyl-D-aspartate (NMDA) subtype of excitatory amino acid receptors, the protection given by a non-competitive (MK-801) and a competitive (CGP 39551) NMDA receptor antagonist against the loss of glutamatergic and gamma-amino butyric acid (GABAergic) neurochemical markers was compared. Appropriate doses of both compounds (1 mg/kg MK-801 and 25 mg/kg CGP 39551) completely reversed the decrease of high affinity uptake of glutamate and activity of glutamate decarboxylase in the olfactory cortex, amygdala, hippocampus and lateral septum. In addition, they also essentially counteracted the increase of a glial marker, the enzyme glutamine synthetase, consequent to neuronal degeneration. The results confirmed that involvement of NMDA receptors is essential for the full expression of neuropathological effects of kainic acid. They also support the use of a competitive antagonist of the NMDA receptor, such as CGP 39551, to afford substantial protection against the excitotoxic damage, whilst giving fewer side effects and motor disturbances than MK-801.

2-Amino-5-phosphonovalerate↗
PubMed1991

Postnatal maturation of cholinergic markers in forebrain regions of C57BL/6 mice.

The maturation of some neurochemical markers linked to cholinergic function (choline acetyltransferase, acetylcholinesterase, muscarinic binding sites) has been studied from 10 to 150 days of age in mice belonging to C57BL/6 strain. Previous studies had suggested that part of the cholinergic neurons of the basal forebrain undergo degeneration during juvenile stages of life in these rodents. Our data showed a delayed maturation of the cholinergic levels in the cortex and hippocampus, the main targets of the forebrain cholinergic neurons, but not in the striatum and superior colliculus. In none of these regions was any clear trend towards a decrement of cholinergic levels observed during the lifespan considered. In the medial septum-diagonal band area, an actual decrease of cholinergic levels was observed between 60 and 150 days of age. A side experiment based on daily administration of GM1 ganglioside during juvenile life, showed no effect of this treatment on the maturation of cholinergic markers.

Acetylcholinesterase↗
PubMed1991

Temporal, regional and cellular selectivity of neonatal alteration of the thyroid state on neurochemical maturation in the rat.

The effects of alteration of thyroid state on neurochemical maturation have been studied in rats made hypothyroid by daily injections of methimazole or hyperthyroid by daily supplementation with thyroid hormone (T3) from postnatal days 1 to 27. Biochemical assays on seven brain regions plus the spinal cord were carried out on 14 and 28 day-old rats as well as in adult rats after at least 40 days of recovery. 2',3'cyclic nucleotide phosphohydrolase (CNPase), a specific marker for oligodendrocytes and myelination was significantly decreased in all regions except the spinal cord of hypothyroid rats. The astrocytic marker glutamine synthetase (GS) was slightly increased in the hippocampus of hypothyroid rats. Choline acetyltransferase (ChAT), a specific marker for cholinergic neurons, was decreased in the prefrontal and visual cortices, the striatum and the superior colliculus and increased in the cerebellum of hypothyroid rats; in addition, the enzyme activity was increased in the prefrontal cortex and striatum and decreased in the cerebellum of hyperthyroid rats. Acetylcholinesterase (AChE) activity was decreased in the prefrontal cortex and in the striatum of hypothyroid rats while 3H-quinuclidinyl benzilate (QNB) muscarinic binding was decreased in all cortical areas and in the hippocampus of hypothyroid rats. Glutamate decarboxylase (GAD), a specific marker for GABAergic neurons, was decreased in the cortical areas of hypothyroid rats. Aromatic amino acid decarboxylase (AAD), a general marker for monoaminergic neurons, was unaffected. Alteration of neurochemical parameters was never observed in the spinal cord. Under our experimental conditions, the effects of alteration of thyroid state appeared graded and selective with respect to temporal, regional and cellular parameters.

2',3'-Cyclic-Nucleotide Phosphodiesterases↗
PubMed1991

Temporary impairment of Müller cell metabolism in the rat retina by intravitreal injection of fluorocitrate.

Fluorocitrate was injected in the vitreum of rats in order to define the experimental conditions for a temporary impairment of Müller cell metabolism in the retina. Injection of 16 nmol of fluorocitrate appeared to fulfil this requirement since this dose resulted in a large decrease in retinal endogenous glutamine and a smaller decrease in glutamate within 6 hr of administration. The reversible nature of the effect was attested by a substantial recovery of the retinal levels of the two amino acids within 24 hr of injection. In vitro experiments of carbon incorporation from different substrates, carried out with retinas dissected from eyes previously injected with fluorocitrate, were consistent with a metabolic impairment of glial cells, since carbon incorporation from [14C]acetate into glutamine was almost completely abolished in the fluorocitrate-treated retinas. Electron microscopic examination in fluorocitrate-poisoned retinas demonstrated essentially selective ultrastructural alterations of Müller cells at times corresponding to their maximal metabolic impairment. Since Müller cells are by far the largest glial population of the rat retina, common astrocytes being only scattered in the nerve fibre layer, the present experimental model may be used to study the role of Müller cells in the metabolism of retinal neurotransmitters.

Animals↗
PubMed1990

Anatomical and neurochemical evidence for suicide transport of a toxic lectin, volkensin, injected in the rat dorsal hippocampus.

Volkensin, a ribosome-inactivating toxic lectin which has been proposed as a 'suicide transport' agent in the CNS, was unilaterally injected in the rat dorsal hippocampus at a dose of 1.2 ng. Three to 5 days after the injection, degenerating neurons were observed at the electron microscope in the medial septum-diagonal band area ipsilateral to the injection. Ten days after the injection, the number of pyramidal neurons in the CA3 region of the contralateral hippocampus, which are the major source of hippocampal commissural fibers, was obviously decreased. At the same survival time, the number of choline acetyltransferase (ChAT) immunoreactive neurons in the ipsilateral medial septum-diagonal band area was moderately but significantly decreased. These neurons are known to be the major source of the septohippocampal cholinergic projection. Concomitantly, microchemical assays of ChAT levels revealed a 25% decrease of enzyme activity in the medial septum-diagonal band area ipsilateral to the injection. This was accompanied by a 33% decrease of ChAT in the ipsilateral ventral hippocampus which was interpreted to be due, at least in part, to the degeneration of cholinergic septal neurons projecting to both the dorsal and the ventral hippocampus. Taken together, these results provide clear evidence that volkensin is taken up by nerve terminals in the injected area of the brain and retrogradely transported to the cell bodies originating the projection, which are killed by the toxin. The usefulness of the strategy of 'suicide transport' in the CNS is, therefore, confirmed.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Effects of short- and long-term ganglioside treatment on the recovery of neurochemical markers in the ibotenic acid-lesioned rat striatum.

The striatum of adult rats was bilaterally lesioned with stereotaxic injections of ibotenic acid in a dose (16 nmoles) that resulted in subtotal lesions. Some rats received systemic ganglioside treatment starting the day before operation and lasting for 6 or 24 days after operation; they were compared with lesioned rat receiving systemic saline injections as well as with corresponding groups of sham-operated animals. Specific neurochemical markers for cholinergic neurons (choline acetyltransferase, ChAT), GABAergic neurons (glutamate decarboxylase; GAD), and astrocytes (glutamine synthetase; GS) were assayed to asses the neurochemical recovery promoted by ganglioside treatment. Twenty-four, but not six, days after operation a significant increase of ChAT and GAD was measured in the striatum of lesioned rats treated with gangliosides in comparison with the saline group. Furthermore, a significant increase of both enzymes occurred in the striatum of lesioned rats receiving ganglioside treatment for 24 days in comparison with rats receiving ganglioside treatment for 6 days only. A small but significant increase of ChAT was measured in the striatum of sham-operated rats after 24 days of ganglioside treatment in comparison with the corresponding saline group. Finally, the increase of GS caused by the glial reaction to the ibotenic acid lesion was not affected by ganglioside treatment. The results indicate that a relatively long-lasting ganglioside treatment stimulates the recovery of specific neuronal transmitter markers and that some effect is, in addition, exerted on unlesioned cholinergic striatal neurons.

Animals↗
PubMed1990

Regional maturation of neurotransmitter-related and glial markers during postnatal development in the rat.

Neurotransmitter-related (choline acetyltransferase, acetylcholinesterase, glutamate decarboxylase, L-glutamate and GABA high affinity uptake) and glial neurochemical markers (glutamine synthetase, beta-alanine uptake and 2',3' cyclic nucleotide phosphohydrolase) have been quantitatively assayed in various regions of the rat CNS during normal postnatal development: spinal cord, cerebellum, superior colliculus, hippocampus, striatum, visual cortex, frontal sensory-motor cortex and prefrontal cortex. In general, neurochemical markers show an obvious trend toward increasing levels in parallel with brain maturation. However, some relevant exceptions have been observed and discussed. Detailed knowledge of regional neurochemical brain maturation is important since it gives us information concerning some key events of brain development. In addition, this knowledge is the essential pre-requisite for studies aimed at the alteration of specific regional and temporal parameters through experimental manipulation.

2',3'-Cyclic-Nucleotide Phosphodiesterases↗
PubMed1990

Developmental profiles of cholinergic activity in the habenulae and interpeduncular nucleus of the rat.

Choline acetyltransferase (ChAT) was measured in the habenula and in the interpeduncular nucleus of rats from 1 to 12 weeks of age. A remarkable degree of parallelism was shown by the developmental curves in the two nuclei. In both cases the highest level of enzyme activity was reached at 3 weeks of age and was followed by some decrease towards adult values. A statistically highly significant correlation was demonstrated between ChAT levels in the two nuclei at the various developmental stages. The rise of the cholinergic marker was slightly advanced in the habenula in comparison with the interpeduncular nucleus. The present data may be useful for studies focused on neonatal synaptogenesis, plasticity and synaptic neurochemistry of this relatively simple model of brain connections.

Aging↗
PubMed1989

Gangliosides attenuate NMDA receptor-mediated excitatory amino acid release in cultured cerebellar neurons.

Release of both D-[3H]aspartate and endogenous amino acids was measured in primary cultures of cerebellar granule cells. Two hour-pretreatment with the glycosphingolipids, GM1 or GT1b, attenuated the stimulation of excitatory amino acid release induced by depolarizing concentrations of K+ (50 mM). Gangliosides inhibited the phencyclidine (PCP)-sensitive component of depolarization-induced release, i.e. the amplification of release that follows activation of NMDA receptors by the endogenous glutamate.

Amino Acids↗