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Abstract

In the extraocular muscles of guinea pig, two types of muscle fibres with different modes of electrical activity can be distinguished. One type, showing MEPPs,of short and invariable duration, is capable of generating action potential in response to stimulation of its innervating nerve, while in the other showing MEPPs of slower and variable duration, no action potential can be generated under similar condition of stimulation. With the method of cholinesterase staining and electrophoretic marking by pontamine sky blue the two types of electrical activity can be shown to originate respectively from the fast muscle fibres with a single neuromuscular junction and the slow muscle fibres with multiple junctions. From two-microelectrode voltage-clamp experiments, the time constant(:)of decay of MEPCs and its voltage coefficient (A) of the fast and the slow muscle fibres are calculated. It is shown that (1) near the resting potential of the fibres, the value of #tau# of slow fibres is longer than that of fast ones; (2) the value of A of slow fibres is much smaller than that of fast ones, i. e. the value of i of slow fibres undergoes
less change with change of membrane potential. Possible mechanisms underlying
the genesis of the different electrical activities of the two types of muscle fibres are discussed.

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Citing This Article：

. . Acta Physiol Sin 1987; 39 (4): (in Chinese with English abstract).