Biomaterial Database

[PTZ-induced paroxysmal depolarization shift on Helix p. neurons: mechanism of plateau and pacemaker potentials (author's transl)]. 1975

C Ducreux, and M Gola

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.

UI	MeSH Term	Description	Entries
D008564	Membrane Potentials	The voltage differences across a membrane. For cellular membranes they are computed by subtracting the voltage measured outside the membrane from the voltage measured inside the membrane. They result from differences of inside versus outside concentration of potassium, sodium, chloride, and other ions across cells' or ORGANELLES membranes. For excitable cells, the resting membrane potentials range between -30 and -100 millivolts. Physical, chemical, or electrical stimuli can make a membrane potential more negative (hyperpolarization), or less negative (depolarization).	Resting Potentials,Transmembrane Potentials,Delta Psi,Resting Membrane Potential,Transmembrane Electrical Potential Difference,Transmembrane Potential Difference,Difference, Transmembrane Potential,Differences, Transmembrane Potential,Membrane Potential,Membrane Potential, Resting,Membrane Potentials, Resting,Potential Difference, Transmembrane,Potential Differences, Transmembrane,Potential, Membrane,Potential, Resting,Potential, Transmembrane,Potentials, Membrane,Potentials, Resting,Potentials, Transmembrane,Resting Membrane Potentials,Resting Potential,Transmembrane Potential,Transmembrane Potential Differences
D008959	Models, Neurological	Theoretical representations that simulate the behavior or activity of the neurological system, processes or phenomena; includes the use of mathematical equations, computers, and other electronic equipment.	Neurologic Models,Model, Neurological,Neurologic Model,Neurological Model,Neurological Models,Model, Neurologic,Models, Neurologic
D009474	Neurons	The basic cellular units of nervous tissue. Each neuron consists of a body, an axon, and dendrites. Their purpose is to receive, conduct, and transmit impulses in the NERVOUS SYSTEM.	Nerve Cells,Cell, Nerve,Cells, Nerve,Nerve Cell,Neuron
D010433	Pentylenetetrazole	A pharmaceutical agent that displays activity as a central nervous system and respiratory stimulant. It is considered a non-competitive GAMMA-AMINOBUTYRIC ACID antagonist. Pentylenetetrazole has been used experimentally to study seizure phenomenon and to identify pharmaceuticals that may control seizure susceptibility.	Leptazole,Pentamethylenetetrazole,Pentetrazole,Cardiazol,Corasol,Corazol,Corazole,Korazol,Korazole,Metrazol,Metrazole,Pentazol,Pentylenetetrazol
D011188	Potassium	An element in the alkali group of metals with an atomic symbol K, atomic number 19, and atomic weight 39.10. It is the chief cation in the intracellular fluid of muscle and other cells. Potassium ion is a strong electrolyte that plays a significant role in the regulation of fluid volume and maintenance of the WATER-ELECTROLYTE BALANCE.
D006372	Helix, Snails	A genus of chiefly Eurasian and African land snails including the principal edible snails as well as several pests of cultivated plants.	Helix (Snails),Snails Helix
D000818	Animals	Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA.	Animal,Metazoa,Animalia
D012908	Snails	Marine, freshwater, or terrestrial mollusks of the class Gastropoda. Most have an enclosing spiral shell, and several genera harbor parasites pathogenic to man.	Snail
D013696	Temperature	The property of objects that determines the direction of heat flow when they are placed in direct thermal contact. The temperature is the energy of microscopic motions (vibrational and translational) of the particles of atoms.	Temperatures