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Biomedical subjects

M Gola

Publications and source records attributed to M Gola.

At least 91 records · Page 5Linked to original sources
PubMed1984

A re-excitation mechanism for strychnine-induced doublets in molluscan neurons.

The effects of strychnine on Aplysia R2 neurons were evaluated using simultaneous intracellular recordings of the soma and axon potentials. 1 mM strychnine produced a slight enlargement of the somatic spike and a large increase of the axon spike duration. Following direct stimulation, the soma displayed depolarizing afterpotentials ( DAPs ) which might trigger extra-spikes, both produced electronically by long-lasting axon spikes. Cobalt suppressed both the axon spike lengthening and the somatic extra-spikes or DAPs , and induced large depolarizing shifts in the soma. The region of largest spike lengthening (proximal axon) had a large density of Ca channels. The different effects of strychnine on the soma and on the axon were assumed to result from a selective blockage of the V-dependent K channels which would predominate in the axon whereas Ca-activated K channels would predominate in the soma.

Action Potentials↗
PubMed1983

Two identified interneurons modulate the firing pattern of pacemaker bursting cells in Helix.

Two interneurons modulating the firing pattern of two endogeneous bursting neurons have been identified in the visceral ganglion. They are characterized by large depolarizing afterpotentials and doublets due to the delayed firing of a dense layer of terminal processes converging onto the axon branches from the two bursters. Firing of the terminal processes upon soma or axon stimulation needs either subthreshold depolarization of the cell or conditioning nerve stimulation acting as a gating mechanism.

Animals↗
PubMed1977

Ba++ induced square-shaped potential waves in molluscan neurones.

Rhythmic slow square-shaped potential waves lasting 20-50 sec are induced in Aplysia neurones when Ca++ is replaced by Ba++. During the plateau, the membrane is highly permeable to Ba++ ions, whereas in the interwave period the membrane resistance increases by 60 times. Analysis with slow current ramps suggests that the membrane properties of Ba-treated neurones and normally burst-generating neurones are similar.

Action Potentials↗
PubMed1976

Slow current changes underlying square shaped potential waves in warmed Aplysia neurones.

On warming, the regularly firing L11 neurone of Aplysia turns into a bursting-type neurone. The bursts of spikes are produced by slow square waves which can also be obtained at room temperature by adding TTX or Co++. Experiments with slow ramp voltage clamp show that warming induces a negative slope (or negative resistance) on the current-voltage characteristic and very slow current variations (r = 10 to 50 sec) in response to potential changes. The square waves are explained by these two phenomena.

Animals↗
PubMed1975

[PTZ-induced paroxysmal depolarization shift on Helix p. neurons: mechanism of plateau and pacemaker potentials (author's transl)].

The convulsant pentylenetetrazol (PTZ), 1% induces paroxysmal depolarization shifts (PDS) on regularly firing neurones of Helix. Synaptic or antidromic stimulation or transmembrane current produces PDSs followed by a refractory period. For 5% of PTZ-treated neurons the membrane depolarizes up to -15 mV and PDS can be obtained by injected inward current. In voltage clamp experiments the steady i equals f(V) characteristic of PTZ-treated neurons is N-shaped with a current flowing inwardly between -45 and -15 mV. The negative conductance is enhanced by warming and disappears at temperatures lower than 15 degrees C. Besides, a slow triangular function (less than or equal to 10 mV/sec) applied to the voltage clamp system indicates an important hysteresis in the i equals f(V) curves according to the direction of sweeping: depolarization or repolarization. From a hyperpolarized state (-70 mV) the stable point of the N-shaped i equals f(V) characteristic is at -15 mV bringing the membrane potential to this level. From a depolarized state congruent to 10 mV) the i equals f(V) characteristic shows no local negative slope and the stable point is at -45 mV bringing the membrane potential down to this level. PDSs correspond to the voltage transition between these two stable points. The amplitude of PDSs is directly related to the amplitude of hysteresis and their frequency to the kinetics of the i equals f(V) characteristics. The different modes of activity under PTZ are explained by the position of the i equals 0 axis in relation with the region of negative resistance. It is suggested that increase of K+ -inactivation by PTZ is the main phenomenon leading to a N-shaped characteristic.

Animals↗