Biomaterial Database

Transmembrane potential changes caused by shocks in guinea pig papillary muscle. 1996

X Zhou, and W M Smith, and D L Rollins, and R E Ideker

Department of Medicine, Duke University Medical Center, Durham, North Carolina 27710, USA.

To study transmembrane potential (Vm) changes (delta Vm) caused by extracellular field stimulation, Vm was recorded in 10 guinea pig papillary muscles by a double-barrel microelectrode. A 10-ms shock was delivered during the action potential plateau or during diastole. Six shock strengths (1.8 +/- 0.4, 3.8 +/- 0.7, 5.6 +/- 0.9, 7.2 +/- 1.1, 11.1 +/- 1.9, and 17.8 +/- 1.5 V/cm) were given with both polarities. The tissue was then treated with either 30 microM tetrodotoxin (TTX; n = 5) or 30 microM TTX plus Ca(2+)-free (n = 5) perfusion. For shocks during the action potential plateau, delta Vm caused by the six potential gradients was 22.4 +/- 9.6, 43.6 +/- 17.4, 54.7 +/- 17.9, 60.4 +/- 18.1, 65.4 +/- 13.7, and 66.4 +/- 12.2 mV for shocks causing depolarization and 41.1 +/- 16.5, 68.3 +/- 22, 80.5 +/- 20.4, 84.0 +/- 19.5, 93.6 +/- 16.3, and 98.9 +/- 15.4 mV for shocks causing hyperpolarization. The relationship between delta Vm and shock potential gradient was not linear. During diastole, hyperpolarizing shocks induced initial hyperpolarization, then depolarization followed again by hyperpolarization. A new depolarization upstroke occurred immediately after the shock. After TTX or TTX plus Ca(2+)-free perfusion, point stimuli 10 times diastolic threshold could not induce an action potential, but a shock field of 1.8 +/- 0.2 V/cm still induced action potentials. The peak value of depolarization measured with respect to resting potential (-87 +/- 5 mV) during the hyperpolarizing shock decreased from +14 +/- 22 before to -66 +/- 30 mV with TTX perfusion (P < 0.01). The fast upstroke rate of depolarization both during and immediately after the end of hyperpolarizing shocks was inhibited by TTX perfusion. Thus 1) the relationship between delta Vm and shock potential gradient is not linear; 2) field but not point stimulation can induce an action potential when Na+ channels are inactivated; and 3) during diastole Na+ channels are activated twice by a 10-ms hyperpolarizing shock, once during shock-induced hyperpolarization and again immediately after the end of the shock.

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
D010210	Papillary Muscles	Conical muscular projections from the walls of the cardiac ventricles, attached to the cusps of the atrioventricular valves by the chordae tendineae.	Muscle, Papillary,Muscles, Papillary,Papillary Muscle
D010477	Perfusion	Treatment process involving the injection of fluid into an organ or tissue.	Perfusions
D011930	Reaction Time	The time from the onset of a stimulus until a response is observed.	Response Latency,Response Speed,Response Time,Latency, Response,Reaction Times,Response Latencies,Response Times,Speed, Response,Speeds, Response
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
D004597	Electroshock	Induction of a stress reaction in experimental subjects by means of an electrical shock; applies to either convulsive or non-convulsive states.	Electroconvulsive Shock,Electroconvulsive Shocks,Electroshocks,Shock, Electroconvulsive,Shocks, Electroconvulsive
D006168	Guinea Pigs	A common name used for the genus Cavia. The most common species is Cavia porcellus which is the domesticated guinea pig used for pets and biomedical research.	Cavia,Cavia porcellus,Guinea Pig,Pig, Guinea,Pigs, Guinea
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
D013779	Tetrodotoxin	An aminoperhydroquinazoline poison found mainly in the liver and ovaries of fishes in the order TETRAODONTIFORMES, which are eaten. The toxin causes paresthesia and paralysis through interference with neuromuscular conduction.	Fugu Toxin,Tarichatoxin,Tetradotoxin,Toxin, Fugu