Biomaterial Database

Two different ionic mechanisms generating the spike "positive" afterpotential in molluscan neurons. 1967

D J Chiarandini, and E Stefani

The ionic bases of the "positive" afterpotential (ap) have been examined in the so-called DInhi neurons of the central nervous system of Cryptomphallus aspersa. In these cells E(K) has been determined and its value compared with the equilibrium, potential of the ap (E(ap)). It has been found that in half of the studied cells the E(K) value is very close to E(ap) whereas in another half, the difference (E(K) - E(ap)) is large and amounts to circa -10 mv. The effects of changes in the concentration gradients of K(+), Cl(-), and Na(+) were assayed in both groups of cells. When the [K(i)/[K](o) ratio is reduced in both groups of neurons, the ap amplitude and the E(ap) diminished. In cells displaying a large (E(K) - E(ap)), Cl-free Ringer's solution diminished the ap amplitude and E(ap), but produced no effect in the neurons with a reduced (E(K) - E(ap)). A similar effect was observed if [Cl], was increased by intracellular injection of NaCl. Changes in both [Na](o) and [Na](i) were ineffective. It is concluded that K(+) is the only ion involved in the origin of the ap in the groups of cells with a low value for (E(K) - E(ap)). On the contrary, the ap of the neurons presenting large (E(K) - E(ap)) is produced by a simultaneous increase in the fluxes of both K(+) and Cl(-).

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
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
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.
D002490	Central Nervous System	The main information-processing organs of the nervous system, consisting of the brain, spinal cord, and meninges.	Cerebrospinal Axis,Axi, Cerebrospinal,Axis, Cerebrospinal,Central Nervous Systems,Cerebrospinal Axi,Nervous System, Central,Nervous Systems, Central,Systems, Central Nervous
D002712	Chlorides	Inorganic compounds derived from hydrochloric acid that contain the Cl- ion.	Chloride,Chloride Ion Level,Ion Level, Chloride,Level, Chloride Ion
D004594	Electrophysiology	The study of the generation and behavior of electrical charges in living organisms particularly the nervous system and the effects of electricity on living organisms.
D000200	Action Potentials	Abrupt changes in the membrane potential that sweep along the CELL MEMBRANE of excitable cells in response to excitation stimuli.	Spike Potentials,Nerve Impulses,Action Potential,Impulse, Nerve,Impulses, Nerve,Nerve Impulse,Potential, Action,Potential, Spike,Potentials, Action,Potentials, Spike,Spike Potential
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
D012964	Sodium	A member of the alkali group of metals. It has the atomic symbol Na, atomic number 11, and atomic weight 23.	Sodium Ion Level,Sodium-23,Ion Level, Sodium,Level, Sodium Ion,Sodium 23