The resting membrane potential of the somatic muscle cells of Ascaris lumbricoides

Abstract

1. The resting membrane potential of Ascaris muscle fibres, which is normally relatively insensitive to ion changes in the medium, has been measured under a wide variety of conditions. 2. The results have been interpreted in terms of a form of the constant field equation containing additional terms for the contribution of ions and charged groups other than potassium, sodium and chloride. 3. Normally the contribution of the additional terms is large and tends to outweigh the contributions of potassium, sodium and chloride. 4. The contribution of the additional terms is considerably reduced in the absence of sodium and in the presence of γ‐amino butyric acid and acetylcholine. 5. It is suggested that the additional terms may represent the contribution of an electrogenic active transport mechanism to the factors determining the membrane potential.

Studies on the ionic selectivity of the GABA‐operated chloride channel on the somatic muscle bag cells of the parasitic nematode Ascaris suum

“…The theoretical value of EGABA can be calculated by assuming that EGABA is an entirely chloridemediated event and thus will be equal to E,. Using a mean internal chloride concentration of 13 7 mm (as determined by Brading & Caldwell (1971) using flame photometry) and the extracellular chloride concentration, which is assumed to be the same as that of the APF, 107 mm, then the value for E0, calculated from the Nernst equation is -54 mV. This is in close agreement with the value of EG determined in this study which was -54*9 + 0 9 mV in normal APF (n = 62; Fig.…”

A HIGH‐CONDUCTANCE CALCIUM‐DEPENDENT CHLORIDE CHANNEL IN ASCARIS SUUM MUSCLE

“…Del Castillo et al 1964;Brading & Caldwell, 1971). One of the conclusions oftheir work was the fact that membrane potential is not greatly influenced by K but that Cl has a marked effect.…”

ELECTROPHYSIOLOGICAL EFFECTS OF PIPERAZINE AND DIETHYLCARBAMAZINE ON Ascaris suum SOMATIC MUSCLE

“…Diethylcarbamazine also depolarized the membrane in active preparations at 320 to 35°C, but this effect was variable and often absent at 220 to 25°C. The effect of K+ on the resting membrane potential in Ascaris has been reported to be small (Brading & Caldwell, 1971). It is likely that the depolarizing action in active preparations results mainly from an action on the voltage-sensitive K+ conductance rather than from any effect on the resting K+ conductance.…”