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S Vicini

Publications and source records attributed to S Vicini.

At least 91 records · Page 5Linked to original sources
PubMed1988

Subsets of GABAergic neurons in dissociated cell cultures of neonatal rat cerebral cortex show co-localization with specific modulator peptides.

The GABAergic properties of dissociated neurons from cerebral cortex of neonatal rats were studied in primary culture using electrophysiological, biochemical and immunohistochemical methods. Cultured neurons had a resting potential of -50 to -60 mV and exhibited spontaneous excitatory and inhibitory synaptic currents. Non-spontaneous (elicited) ionic currents were produced by direct application of GABA and glutamate. Cultures contained measurable amounts of GABA from the first day in culture; GABA content reached a plateau around the 10th day of culture, and continued, nearly unchanged, until the 21st day of culture. Immunohistochemistry showed that 45% of the total cells in culture contained glutamic acid decarboxylase (GAD). Octadecaneuropeptide (ODN), a putative neuroregulatory peptide for benzodiazepine recognition sites, was present in approximately 28% of all neurons. Ninety-three percent of ODN-positive cells demonstrated GABAergic properties as well by displaying GAD-immunoreactivity. The peptide GABA-modulin (GM), a putative GABA receptor modulator, was found in about 75% of all neurons, with a further 65% of these cells exhibiting GAD-immunoreactivity. Cells immunopositive for neuropeptide Y (NPY), somatostatin (SRIF), and cholecystokinin-octapeptide (CCK), were found at much lower incidence (1-4%). Double-labelling studies showed that 90-97% of the cells positive for NPY, SRIF and CCK were also positive for GAD. Cells immunoreactive with serotonin or tyrosine hydroxylase were not detected. We suggest that primary cultures of neonatal cortical neurons may provide a useful experimental model to investigate the function and the modulation of GABAergic neurotransmission in the cerebral cortex.

Animals↗
PubMed1988

Phencyclidine and glycine modulate NMDA-activated high conductance cationic channels by acting at different sites.

Glutamate activates high (40-50 pS) and low (5-15 pS) conductance cationic channels in outside-out patches excised from cultured cortical and cerebellar granule neurons of neonatal rats. In these neurons, the excitatory amino acid N-methyl-D-aspartic acid (NMDA) activates mainly high conductance channels. Phencyclidine (PCP) at 2 microM selectively reduces the number of NMDA-activated channel openings, at 20 microM it reduces the channel open-time. Glycine increases the opening frequency of high conductance NMDA-activated channels. This action is counteracted by PCP. This inhibition by PCP can be eliminated by reversing the polarity of the membrane patch. However, the effect of glycine is voltage independent. These results imply different sites of action for these two modulators.

Animals↗
PubMed1988

Voltage-dependent block by strychnine of N-methyl-D-aspartic acid-activated cationic channels in rat cortical neurons in culture.

Single-channel currents were recorded by means of the patch clamp method in outside-out patches excised from rat cortical neurons in primary culture. The excitatory amino acid N-methyl-D-aspartic acid activated mainly 40-50 pS conductance channels. Channel opening durations were characterized by a series of rapid openings and closures induced by the presence of Mg2+ ions. This inhibitory effect was voltage dependent. Strychnine, the antagonist of the glycine-gated Cl- channels, blocks the N-methyl-D-aspartic acid-activated cationic channel in cultured rat cortical neurons. Strychnine action is voltage dependent and it is not counteracted by ethylenediaminetetraacetic acid, ruling out Mg2+ contamination of strychnine. It has been reported recently that glycine increases the rate of openings of N-methyl-D-aspartic acid-activated channels. This action is not affected by the presence of strychnine. Our results show that 1) Mg2+ and strychnine have an apparently similar intermediate blocking action on the NMDA-activated channels, 2) strychnine presumably acts as a sequential open channel blocker producing a different type of block compared with the one reported for Mg2+ ions, and 3) the lack of effect of strychnine on the glycine potentiation of the N-methyl-D-aspartic acid response indicates that this alkaloid does not competitively antagonize glycine but acts as an open channel blocker.

Allosteric Regulation↗
PubMed1988

Development and survival of neurons in dissociated fetal mesencephalic serum-free cell cultures: I. Effects of cell density and of an adult mammalian striatal-derived neuronotrophic factor (SDNF).

The use of CNS cultures for detection and quantification of neuronotrophic activity in the CNS has been analyzed. In particular the development, i.e., neurotransmitter uptake characteristics, and survival of dopaminergic and GABAergic neurons in fetal mouse (E13)-dissociated mesencephalic cells cultured in serum-free, hormone-supplemented medium have been assessed as a function of culture time and cell density. At all times, more than 98% of the cells were classified as neurons on the basis of immunocytochemical criteria. Results indicate that the increase of cell density in vitro significantly enhances specific high-affinity dopamine uptake per dopaminergic cell and cell survival. This effect is not limited to the dopaminergic cells and suggests that the development of neurotransmitter-related traits and cell survival are influenced by cell density-derived trophic signals. The above-mentioned cultures and parameters have also been used to detect neuronotrophic activity in adult mammalian brain extracts or more purified preparations. In particular, bovine striatal extracts contain activity capable of increasing high-affinity neurotransmitter uptake parameters and cell survival of at least the dopaminergic and GABAergic neurons present in the culture system. The neuronotrophic activity from bovine striatum has been partially purified and is associated with a fraction whose main component is a basic protein of approximately 14 kDa.

Animals↗
PubMed1987

A pyridazinyl derivative of gamma-aminobutyric acid (GABA), SR 95531, is a potent antagonist of Cl- channel opening regulated by GABAA receptors.

The antagonistic effects of a pyridazinyl derivative of GABA (SR 95531) were investigated on GABA-induced Cl- currents in neonatal rat cortical neurons in primary culture. Three different methods were used: direct application of GABA onto the cell, induction of inhibitory postsynaptic currents (IPSCs) and membrane patch-clamp recordings. Using the first technique, SR 95531 appeared to be more potent than bicuculline methiodide while both drugs seemed equally potent in reducing the IPSC amplitudes and the opening rate of Cl- channels regulated by GABAA receptors in patch-clamp membranes.

Animals↗
PubMed1987

Actions of benzodiazepine and beta-carboline derivatives on gamma-aminobutyric acid-activated Cl- channels recorded from membrane patches of neonatal rat cortical neurons in culture.

Using the patch-clamp, single-channel recording technique, the authors determined conductance and kinetics of gamma-aminobutyric acid-activated Cl- channels recorded from membrane patches excised from neonatal rat cortical neurons in primary culture. The anxiolytic benzodiazepine flunitrazepam increased the channel opening frequency, but it did not change conductance or channel opening burst duration. The anxiogenic compound methyl-6,7-dimethoxy-4-ethyl-beta-carboline-3-carboxylate decreased gamma-aminobutyric acid-activated Cl- channel opening frequency without changing conductance or opening duration. An increase and decrease in the number of channel bursts were elicited by flunitrazepam and methyl-6,7-dimethoxy-4-ethyl-beta-carboline-3-carboxylate, respectively. The effects of both drugs were antagonized by ethyl-8-fluoro-5,6-dihydro-5-methyl-6-oxo-4H-imidazo[1,5][1,4] -benzodiazepine-3-carboxylate (flumazenil), a benzodiazepine antagonist, which per se failed to modify Cl- channel kinetics and conductance.

Animals↗
PubMed1987

A steroid anesthetic prolongs inhibitory postsynaptic currents in cultured rat hippocampal neurons.

Whole-cell patch-clamp recordings were made from cultured rat hippocampal neurons to examine the effects of the steroidal general anesthetic alphaxalone (3 alpha-hydroxy 5 alpha-pregnane 11,20-dione) on responses to pharmacologically applied and physiologically released GABA. At low micromolar concentrations in the anesthetic range, alphaxalone potentiated Cl- conductance responses elicited by GABA and also prolonged evoked GABA-mediated postsynaptic potentials. Under voltage clamp at -40 mV, rapid outwardly directed synaptic currents were evoked that decayed with single exponential kinetics; mean decay time constant was 24 msec at room temperature. Alphaxalone prolonged the decay of these inhibitory postsynaptic currents by 5- to 8-fold, with no increase in peak amplitude or change in growth time. This substantial prolongation of GABA-mediated inhibitory synaptic conductance at clinically effective concentrations may contribute significantly to the anesthetic activity of alphaxalone.

Anesthetics↗
PubMed1986

Pharmacological modulation of GABAergic transmission in cultured cerebellar neurons.

GABA activates specific ion channels in post-natal cerebellar neurons in primary culture generating Cl- currents that can be recorded with the whole-cell patch-clamp technique. Evoked and spontaneous GABA-mediated synaptic activity can be recorded from cells kept in culture for a few days. Benzodiazepine and beta-carboline derivatives which bind with high affinity to the domains for allosteric regulation of GABA receptors facilitated and inhibited directly applied GABA responses and synaptically evoked Cl- currents recorded under voltage-clamp.

Animals↗
PubMed1986

Modulation of gamma-aminobutyric acid-mediated inhibitory synaptic currents in dissociated cortical cell cultures.

Inhibitory gamma-aminobutyric acid-mediated synaptic currents were studied in dissociated primary cultures of neonatal rat cortex with the whole-cell patch-clamp technique. Immunocytochemical staining of the cultures showed the presence of a large number of glutamic acid decarboxylase-containing neurons, and electrical stimulation of randomly selected neurons produced in many cases chloride-mediated and bicuculline-sensitive inhibitory synaptic currents in postsynaptic cells. The amplitude and decay time of the inhibitory synaptic currents were increased by flunitrazepam and decreased by the beta-carboline derivative methyl 6,7-dimethoxy-4-ethyl-beta-carboline-3-carboxylate, two high-affinity ligands for the allosteric regulatory sites of gamma-aminobutyric acid receptors. The imidazobenzodiazepine Ro 15-1788, another high-affinity ligand of the gamma-aminobutyric acid receptor regulatory sites that has negligible intrinsic activity, blocked the action of flunitrazepam and beta-carboline. However, Ro 15-1788 also increased the decay rate of the inhibitory synaptic currents. This might suggest that an endogenous ligand for the benzodiazepine-beta-carboline binding site is operative in gamma-aminobutyric acid-mediated synaptic transmission.

Animals↗
PubMed1986

Apparent acetylcholine receptor channel conversion at individual rat soleus end-plates in vitro.

Miniature end-plate currents (m.e.p.c.s.) were recorded extracellularly from individual fibres in neonatal rat soleus muscles for 2-24 h. In agreement with previous studies, the decay phases of m.e.p.c.s at many end-plates were doubly exponential with time constants of approximately 6 ms and approximately 1.5 ms at 21 degrees C. Earlier studies have shown that doubly exponential decays are due to the combined action of embryonic-type acetylcholine (ACh) receptors (AChRs) with long channel open times and adult-type AChRs with brief open times. When individual end-plates with doubly exponential m.e.p.c.s were studied for several hours or more, the relative size of the slow decay component frequently decreased with time. There was no evidence for a corresponding decrease in total m.e.p.c. amplitude. The time constants of the fast and slow components did not change. M.e.p.c. decays were stable at end-plates that were either very mature (small slow decay component) or very immature (small fast decay component). In these cases, the decay phases were virtually singly exponential and the time constant did not change. These data indicate that at end-plates with a mixture of adult-type and embryonic-type channels, the fraction of adult-type AChRs increases with time. This is similar to what occurs at end-plates developing in vivo. The results of ACh noise analysis experiments support this interpretation.

Action Potentials↗
PubMed1986

[Renal adenocarcinoma associated with a polycystic kidney (presentation of a case and review of the literature)].

The Authors report a case of renal neoplasm association to polycystic kidney. The report was quite occasional, as the patient was not aware to be bearer of a renal dysembryopathy, although such a familiarity was existing formerly. The diagnosis was placed subsequently to ascertainments aiming at establishing the origin of a transient arterial hypertension, occurring recently, in absence of any other symptomatology.

Adenocarcinoma↗
PubMed1985

Myasthenic serum selectively blocks acetylcholine receptors with long channel open times at developing rat endplates.

We have examined the physiological effects of antibodies from a highly specific myasthenic serum on acetylcholine receptors at developing rat endplates. The antibodies reduced the amplitude of miniature endplate potentials by 60% in 3- to 6-day-old animals but had no effect after day 14. Between days 7 and 12 the antibodies had an intermediate effect. This is the same period during which acetylcholine receptors with long channel open times (slow channels) disappear and receptors with short open times (fast channels) increase in number. Therefore, we examined the effect of the antibodies at endplates with a mixture of channel types more carefully. At all times tested, both noise analysis and analysis of miniature endplate currents showed that the antibodies reduced slow channel activity selectively. Single-channel recordings indicated that acetylcholine receptors that remained active after antibody treatment had normal gating properties. Thus, the antibodies appeared to silence slow channels selectively.

Animals↗
PubMed1985

Gating properties of acetylcholine receptors at developing rat endplates.

The gating properties of acetylcholine receptors (AChRs) change during the development of rat soleus endplates. During the first 3 weeks after birth, the apparent mean channel open time (tau) decreases severalfold and the single-channel conductance (gamma) increases 50%. To better understand this phenomenon, we used a combination of noise analysis, analysis of miniature endplate currents (MEPCs), and single-channel recordings to quantify the relative levels of fast and slow AChR activity at developing soleus endplates. When the same endplates were studied with both noise analysis and MEPC analysis, results obtained with the two techniques were strongly correlated, but MEPC analysis yielded higher estimates of the relative amount of slow channel activity. Experiments designed to examine the distribution of fast and slow channels gave no evidence for a gradient of either channel type within individual endplates; rather, fast and slow channels appeared to be mixed together. However, the relative amount of fast and slow channel activity did vary markedly among different endplates within individual muscles. In agreement with earlier studies, we found a progressive decrease in the relative amount of slow channel activity during the first 3 weeks after birth. However, our data indicate that this process begins sooner than reported previously and takes longer to complete. Some of the same endplates that were studied physiologically were also examined in the electron microscope to test the hypothesis that changes in AChR gating might be related to ultrastructural changes such as the formation of folds. The physiological and ultrastructural results were essentially uncorrelated.

Age Factors↗