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Mechanical Properties of the Longitudinal and Circular Muscle in the Earthworm
1 Department of Physiology, Faculty of Medicine, Kyushu University Fukuoka, Japan
1. The mechanical properties of the longitudinal and circular muscles of the earthworm, Pheretima communissima, were studied in various solutions.
2. In the longitudinal muscle, field stimulation elicited two distinct waves of tension development, i.e. phasic and tonic contractions. But in the circular muscle, these components were not distinguishable.
3. The phasic contraction in the longitudinal muscle increased in sodium-free (tris) solution while the tonic contraction was abolished. Neither the phasic nor the tonic contraction, however, was influenced by tetrodotoxin (3 x 10-6 M), d-tubocurarine (1.4 x 10-5M), or atropine (3.5 x 10-5 M).
4. The contraction in the circular muscle was suppressed in sodium-free solution and also by tetrodotoxin (3 x 10-6 M), but was not affected by d-tubocurarine (1.4 x 10-5 M) or by atropine (3.5 x 10-5M).
5. It is speculated that the phasic contraction of the longitudinal muscle is triggered by a calcium spike, and the contraction in the circular muscle is preceded by a sodium spike in muscle fibres.
Submitted on December 7, 1970
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