Pregnenolone sulfate antagonizes GABAA receptor-mediated currents via a reduction of channel opening frequency.

Our previous study showed antagonism of GABAA receptor-mediated whole-cell currents by pregnenolone sulfate (PS). Here, the effects of PS, picrotoxin (PTX) and pentobarbital (PB) were tested on GABA-activated single Cl- channels recorded from membrane patches of rat cortical neurons in primary cultures. PS and PTX selectively decreased the opening frequency of the channels, while PB increased mean open time and burst duration without affecting opening frequency.

Kynurenic acid inhibits the activation of kainic and N-methyl-D-aspartic acid-sensitive ionotropic receptors by a different mechanism.

The action of kynurenic acid on currents elicited by the activation of amino acid receptors was investigated in primary cultures of cortical neurons prepared from neonatal rats. Kynurenic acid was tested on currents elicited by both N-methyl-D-aspartic acid (NMDA) and kainate, using patch-clamp recording techniques in "outside-out" and "whole-cell" configurations. The inhibition by kynurenic acid was compared with that elicited by amino-phosphono-valeric acid (APV).

Embryonic acetylcholine receptors guarantee spontaneous contractions in rat developing muscle.

Many proteins are expressed in distinct embryonic and adult forms. However, in most cases we do not know why the embryonic form of proteins is required. This question can be readily addressed for the acetylcholine receptor (AChR) because developmentally specified modifications of this ligand-gated ion channel can be directly related to changes in membrane currents.

Neurosteroid pregnenolone sulfate antagonizes electrophysiological responses to GABA in neurons.

Our earlier biochemical studies suggested that the neurosteroid pregnenolone sulfate (PS) may reduce gamma-aminobutyric acid (GABA) action at the Cl- channel associated with GABAA receptors. In the present electrophysiological study the interaction of PS with the GABAA receptor was tested, using whole-cell voltage-clamp recordings from isolated cerebral cortical neurons of neonatal rats. At micromolar concentrations PS reversibly inhibited GABA-induced current, behaving as an allosteric receptor antagonist.

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.

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.

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.

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.

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.

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.

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.

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.

[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.

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

Miniature end-plate currents (m.e.p.

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.

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.

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.

Neonatal denervation inhibits the normal postnatal decrease in endplate channel open time.

The apparent mean channel open time (tau) of acetylcholine receptors (AChR) at skeletal muscle endplates decreases greater than 3-fold during development. In rat soleus muscles, the change occurs between postnatal days 8 and 18 as channels with long apparent open times (tau = 4.5 msec) disappear while channels with short apparent open times (tau = 1.