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V Taglietti

Publications and source records attributed to V Taglietti.

14 recordsLinked to original sources
PubMed1992

Kinetic and pharmacological properties of high- and low-threshold calcium channels in primary cultures of rat hippocampal neurons.

The kinetic, permeability and pharmacological properties of Ca currents were investigated in primary cultures of rat hippocampal neurons. The low-voltage-activated (LVA) Ca current turned on positive to -60 mV and fully inactivated in a voltage-dependent way. This current was depressed by nickel (Ni, 40 microM) and amiloride (500 microM) and was insensitive to omega-conotoxin (omega-CgTx) (4 microM) and to the Ca agonist Bay K 8644 (5 microM). The high-voltage-activated (HVA) Ca current turned on positive to -40 mV and inactivated slowly and incompletely. This current was much less sensitive than the LVA current to Ni and amiloride but more sensitive to cadmium. omega-CgTx blocked only partially this current (about 50%) in an irreversible way. Bay K 8644 had a clear agonistic action almost exclusively on the omega-CgTx-resistant HVA current component. The present results suggest that the HVA channels, quite homogeneous for their kinetic properties and sensitivity to holding potentials, can be pharmacologically separated in two classes: (i) omega-CgTx-sensitive and Bay-K-8644-insensitive (omega-S/BK-I) and (ii) omega-CgTx-insensitive and Bay-K-8644-sensitive (omega-I/BK-S), the latter displaying a stronger Ca-dependent inactivation.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗
PubMed1992

Calcium currents in solitary hair cells isolated from frog crista ampullaris.

Some properties of Ca2+ currents in hair cells isolated from frog semicircular canals by enzymatic or mechanical treatment were studied by using the whole-cell configuration of the patch-clamp technique. After blocking the large outward K+ currents by substituting Cs+ for K+ and adding tetraethylammonium to the pipette filling solution, voltage- and time-dependent inward currents were clearly detectable in the presence of 4 mM Ca2+ in the extracellular solution. Ca2+ current was recruited at test potentials more positive than -60 mV, showed a rapid activation, and exhibited no inactivation during 150-ms depolarizing pulses. The maximal amplitude was attained at about -20 mV, with an average value of about 80 pA. When Ca2+ in the extracellular solution was replaced with Ba2+, the magnitude of inward currents increased about twofold. Ba2+ currents were blocked more effectively by Cd2+ than by Ni2+, were suppressed by 0.5 microM omega-conotoxin, and were virtually unaffected by amiloride. The dihydropyridine Bay K 8644 caused a marked voltage-dependent increase in inward currents. The present data suggest that hair cells from frog crista ampullaris are endowed with a homogeneous population of Ca2+ channels having several properties similar to those described for neuronal L channels. Since these channels are recruited in a range of potentials close to the resting level, it is suggested that they subserve the control of both resting and evoked transmitter release from the basal pole of the hair cells.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗
PubMed1991

[K+ and Ca++ currents in hair cells isolated from the semicircular canals of the frog].

Hair cells of the inner ear are endowed with different types of ionic channels. To characterize voltage- and ion-dependent channels in vestibular hair cells, experiments were performed in enzymatically isolated hair cells of frog semicircular canals by using the whole-cell configuration of the patch-clamp technique. A large outward current, identified as a K+ current, was recorded when 132 mM KCl were present in the pipette filling solution. It could be dissected pharmacologically into three different components. The first component, which was transient and selectively blocked by 10 mM external 4AP, is most likely an IA-type current. The second one, sensitive to 20 mM external TEA, might be a delayed rectifier K+ current, while the third component insensitive to TEA and showing faster activation time course has been interpreted as a K+ current of IKCa-type. After blocking the outward current by substituting Cs+ for K+ and adding 20 mM TEA to the internal solution, a sustained inward current, identified as a Ca++ current, could be recorded. This current did not inactivate, and was blocked by Cd++ more effectively than Ni++, thus suggesting the presence of Ca++ channels similar to the neuronal "L" channels. Since both K+ and Ca++ channels were recruited at potentials near the resting level, it is suggested that they are involved in the modulation of the resting as well as the evoked transmitter release from the basal pole of the hair cells.

4-Aminopyridine↗
PubMed1990

Pharmacological characterization of voltage-dependent calcium currents in rat hippocampal neurons.

The kinetics and pharmacology of voltage-dependent calcium (Ca) currents in primary cultures of hippocampal neurons were studied using the whole cell clamp technique. The low voltage-activated (LVA) Ca current was activated at -50 mV and completely inactivated within 100 ms. This current was insensitive to omega-conotoxin (omega-CgTx) and to the calcium agonist Bay K 8644. The high-voltage-activated (HVA) Ca current was activated at -20 mV and inactivated incompletely during pulses of 200 ms duration. The snail toxin omega-CgTx revealed two pharmacological components of the HVA Ca current, one irreversibly blocked and the other insensitive to the toxin. Bay K 8644 had a clear agonistic action mainly on the omega-CgTx insensitive component of the HVA Ca current.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗
PubMed1977

Adaptive distortions in the generator potential of semicircular canal sensory afferents.

The generator potential in sensory afferents of frog crista ampullaris was extracellularly recorded from the cut end of the posterior ampullary nerve by means of suction electrodes. A servocontrolled turntable allowed suitable rotatary stimulations. The analysis of the recorded generator potential revealed a different time course from that predicted on the basis of the pendulum model. Adaptation and undershoots in the responses to velocity ramps, steps and sinusoids, were mainly responsible for the deviations, which became very evident only when fairly high acceleration rates were applied. Both adaptation and undershoots were produced presumably by the activation of an electrogenic pump, probably located in nerv terminals contacting the hair cells. In fact, the time course of the generator potential became much more consistent with the predictions from the pendulum model under treatments capable of hindering the ion pump activity.

Acceleration↗
PubMed1976

Effects of Ba ions on frog's isolated muscle spindle.

Dilute solutions of Barium Chloride have been tested on frog's isolated muscle spindles with the aim of clarifying the processes leading to the afferent discharge. In the presence of Ba++ the spindle properties are modified as follows: 1. The discharge of slack spindles increases and becomes extremely regular. 2. The phasic response to stretching is enhanced, the tonic responses being on the contrary virtually suppressed. Under Ba-treatment therefore the spindle changes from a phasic-tonic receptor to a merely phasic receptor. 3. The "silent period" following every propagated spike is prolonged while the safety margin of the "abortive" into propagated spike conversion becomes maximal under Ba-treatment. Additionally, this analysis showed that, when a "true" action potential arises in the spindle, it propagates not only to the stem fibre, but also to all the sensory endings in the spindle intracapsular network. Comparison between the effects of Ba++ and those produced by TEA and ouabain indicates that the action of Ba++ on muscle spindles results from conjunction of two factors : a) reduction of K permeability, and b) enhanced efficiency of an electrogenic Na/K-pump in spindle nerve membranes.

Action Potentials↗
PubMedDate not supplied

[Automatic analysis of M.U.A.P.s (author's transl)].

The authors have studied the Motor Unit Action potentials derived from Extensor Digitorum Brevis and tibialis anterior muscles in normal subjects, using a new method of automatic analysis by means of a digital computer. In the light of the results they have obtained they discuss the validity and the sensitivity of the method as well as the opportuneness of the choice of the muscular region to examine when it comes to determining subclinical or "border-line" cases.

Action Potentials↗