The effects of caffeine on sodium transport, membrane potential, mechanical tension and ultrastructure in barnacle muscle fibres

Previously, the distribution of ammonia between the intracellular and extracellular compartments has been used to predict a significant depolarisation of the resting membrane potential (E(M)) of white muscle from brown trout (Salmo trutta) exposed to a sub-lethal combination of copper and low pH. However, this prediction is based upon two assumptions (i) a relatively high membrane permeability for the ammonium ion with respect to that for ammonia gas and (ii) that this is unaltered by exposure to copper and low pH. Since there is conflicting evidence in the literature of the validity of these assumptions, in the present study E(M) was directly measured in white muscle fibres of trout exposed to copper and low pH (E(M)=−52.2+/−4.9 mV) and compared with that of unexposed, control animals (E(M)=−86.5+/−2.9 mV) (means +/− s.e.m., N=6). In confirming the predicted depolarisation, these data support the hypothesis of electrophysiological impairment as a factor in the reduction in the swimming performance of trout exposed to these pollutants. In addition, the results of this study support the role of a significant permeability of the muscle membrane to NH(4)(+) in determining the distribution of ammonia in fish.

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Force and membrane potential during and after fatiguing, intermittent tetanic stimulation of single Xenopus muscle fibres

Acta Physiologica Scandinavica ◽

10.1111/j.1748-1716.1986.tb07990.x ◽

1986 ◽

Vol 128 (3) ◽

pp. 369-378 ◽

Cited By ~ 53

Author(s):

H. WESTERBLAD ◽

J. LANNERGREN

Keyword(s):

Membrane Potential ◽

Muscle Fibres ◽

Tetanic Stimulation ◽

Stimulation Of

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Thermal acclimation in a crustacean neuromuscular system

Journal of Experimental Biology ◽

10.1242/jeb.98.1.39 ◽

1982 ◽

Vol 98 (1) ◽

pp. 39-47

Author(s):

P. J. Stephens ◽

H. L. Atwood

Keyword(s):

Membrane Potential ◽

Muscle Fibre ◽

Time Constant ◽

Potential Temperature ◽

Shore Crab ◽

Acclimation Temperature ◽

Muscle Fibres ◽

Fibre Membrane ◽

The Pacific ◽

Different Temperatures

1. Effects of temperature on the muscle fibre membrane and synapses of stretcher muscle preparations made from autotomized limbs of the Pacific shore crab (Pachygrapsus crassipes) were investigated. 2. Acclimation of the crabs to different temperatures modified properties of both muscle fibre membrane and synapses. 3. Increased temperature produced an increase in membrane potential of the muscle fibres. A semi-log plot of these data revealed two linear phases of the membrane potential-temperature relationship, with a change in slope near the acclimation temperature. 4. Maximum values for excitatory junction potential (EJP) amplitude and time constant of EJP decay, and minimum values for facilitation were obtained at temperatures close to the acclimation temperature. It is suggested that the decline in EJP amplitude and time constant of decay produced by deviations in temperature from the acclimation temperature is compensated for by an increase in the amount of facilitation. In this way, maximum tension can be produced by the stretcher muscle in a range of at least 8 degrees C around the acclimation temperature.

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