Biomaterial Database

The electrogenic sodium pump and conductance changes in the post-tetanic hyperpolarization of crayfish median giant axons. 1977

M Nagano

The mechanism of post-tetanic hyperpolarization (PTH) occurrence was investigated using the intracellar recording technique. The median giant axon of a crayfish abdominal nerve cord was repetitively stimulated to elicit PTH. When the membrane potential was hyperpolarized by intracellularly applied currents, PTH reversed its sign. K+ removal from the external medium increased the size of PTH and shifted its reversal potential in the hyperpolarizing direction. This results shows that an increase in K+ conductance contributes to the formation of PTH. In a K+-free medium, the size of PTH was reduced by replacement of Na+ with Li+ in the external medium, by application of ouabain or DNP, or by cooling. These procedures shifted the reversal potential in the depolarizing direction. These findings are interpreted as showing that, with K+ absent, PTH is partly due to the activity of electrogenic Na pump. With lowering of external Na+ concentration, PTH became larger and the reversal potential moved in the hyperpolarizing direction. The experiment suggests that Na+ conductance is also increased when PTH is elicited because one expects the amount of Na+ entering per impulse and the activation of the Na pump to be reduced by reducing Na+ concentration in the external medium. It is concluded that PTH in the median giant axons of crayfish is produced by at least two mechanisms. One is an increase in activity of the electrogenic Na pump, and the other is an increase of membrane conductance to K+ and Na+.

UI	MeSH Term	Description	Entries
D008094	Lithium	An element in the alkali metals family. It has the atomic symbol Li, atomic number 3, and atomic weight [6.938; 6.997]. Salts of lithium are used in treating BIPOLAR DISORDER.	Lithium-7,Lithium 7
D010042	Ouabain	A cardioactive glycoside consisting of rhamnose and ouabagenin, obtained from the seeds of Strophanthus gratus and other plants of the Apocynaceae; used like DIGITALIS. It is commonly used in cell biological studies as an inhibitor of the NA(+)-K(+)-EXCHANGING ATPASE.	Acocantherin,G-Strophanthin,Acolongifloroside K,G Strophanthin
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.
D002118	Calcium	A basic element found in nearly all tissues. It is a member of the alkaline earth family of metals with the atomic symbol Ca, atomic number 20, and atomic weight 40. Calcium is the most abundant mineral in the body and combines with phosphorus to form calcium phosphate in the bones and teeth. It is essential for the normal functioning of nerves and muscles and plays a role in blood coagulation (as factor IV) and in many enzymatic processes.	Coagulation Factor IV,Factor IV,Blood Coagulation Factor IV,Calcium-40,Calcium 40,Factor IV, Coagulation
D003080	Cold Temperature	An absence of warmth or heat or a temperature notably below an accustomed norm.	Cold,Cold Temperatures,Temperature, Cold,Temperatures, Cold
D003400	Astacoidea	A superfamily of various freshwater CRUSTACEA, in the infraorder Astacidea, comprising the crayfish. Common genera include Astacus and Procambarus. Crayfish resemble lobsters, but are usually much smaller.	Astacus,Crayfish,Procambarus,Astacoideas,Crayfishs
D004140	Dinitrophenols	Organic compounds that contain two nitro groups attached to a phenol.
D004558	Electric Stimulation	Use of electric potential or currents to elicit biological responses.	Stimulation, Electric,Electrical Stimulation,Electric Stimulations,Electrical Stimulations,Stimulation, Electrical,Stimulations, Electric,Stimulations, Electrical
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
D001369	Axons	Nerve fibers that are capable of rapidly conducting impulses away from the neuron cell body.	Axon