Biomaterial Database

Voltage-clamp analysis of the potassium current that produces a negative-going action potential in Ascaris muscle. 1979

L Byerly, and M O Masuda

1. A voltage clamp has been developed for the pharyngeal muscle of the nematode Ascaris lumbricoides and has been used to analyse the potassium current that produces a negative-going, regenerative action potential in this muscle. 2. Depolarizing voltage steps elicit a sustained inward current; returning the membrane voltage to the resting level evokes a strong, transient, outward current. This outward current reverses direction at the same voltage as that reached by the negative-going spike and is identified as the negative spike current. 3. The negative spike current decays with a time constant of 30 msec at voltages more negative than -30mV. This inactivation of the negative spike conductance is removed by holding the membrane at potentials more positive than -15mV. The time constant for removal of inactivation decreases from more than 300 msec at -15 mV to about 30 msec at +10 mV. 4. When inactivation has been removed, the negative spike conductance is turned on by stepping to potentials more negative than -15 mV. 5. Although the reversal potential for this current depends strongly on [K+]o (42 mV/decade), the potential at which the conductance is turned on is independent of [K+]o. 6. External Na+ seems to facilitate the negative spike current. Reduction of [Na+]o reduces its conductance and shifts the reversal potential to more positive values. 7. External Rb+ and Cs+ show voltage-dependent blocking of this current. 8. This K current is different from all the K currents which have been studied previously; however, it is analogous to the classical Na current of nerve and muscle, except for an inversion of the voltage dependencies.

UI	MeSH Term	Description	Entries
D009132	Muscles	Contractile tissue that produces movement in animals.	Muscle Tissue,Muscle,Muscle Tissues,Tissue, Muscle,Tissues, Muscle
D010609	Pharyngeal Muscles	The muscles of the PHARYNX are voluntary muscles arranged in two layers. The external circular layer consists of three constrictors (superior, middle, and inferior). The internal longitudinal layer consists of the palatopharyngeus, the salpingopharyngeus, and the stylopharyngeus. During swallowing, the outer layer constricts the pharyngeal wall and the inner layer elevates pharynx and LARYNX.	Palatopharyngeus,Muscles of Pharynx,Palatopharyngeal Muscle,Salpingopharyngeus,Stylopharyngeus,Velopharyngeal Muscle,Muscle, Palatopharyngeal,Muscle, Pharyngeal,Muscle, Velopharyngeal,Muscles, Pharyngeal,Pharyngeal Muscle,Pharynx Muscle,Pharynx Muscles
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.
D004553	Electric Conductivity	The ability of a substrate to allow the passage of ELECTRONS.	Electrical Conductivity,Conductivity, Electric,Conductivity, Electrical
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
D001200	Ascaris	A genus of nematodes of the superfamily ASCARIDOIDEA whose species usually inhabit the intestine.	Ascari
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
D066298	In Vitro Techniques	Methods to study reactions or processes taking place in an artificial environment outside the living organism.	In Vitro Test,In Vitro Testing,In Vitro Tests,In Vitro as Topic,In Vitro,In Vitro Technique,In Vitro Testings,Technique, In Vitro,Techniques, In Vitro,Test, In Vitro,Testing, In Vitro,Testings, In Vitro,Tests, In Vitro,Vitro Testing, In