Influence of d-Tubocurarine on Contractile Response of Mammalian Skeletal Muscle in Situ

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Abstract
The effects of close intra-arterial injn. of d-tubocurarine on the contractile response of denervated tibialis anticus muscle evoked by electrical stimulation were studied in anesthetized dogs. Muscle contraction, volume flow of blood limited to this muscle, arterial blood pressure and respiration were recorded continuously. d-Tubocurarine caused a persistent increase in height of contraction usually associated with an initial transient contracture . A very large part, and in many cases all, of this effect must be ascribed to a direct action of d-tubocurarine on the muscle. A secondary decrease in contraction height, rarely demonstrable in these expts., presumably because of the predominance of the augmentative influence, is interpreted as due to a secondary deleterious action of d-tubocurarine on the muscle. The contractile augmentation was very slight or entirely missing in the 2d and subsequent injns. due to a tachyphylactic action of d-tubocurarine on the muscle. Blood flow through the muscle was abruptly increased by a direct vasodilating action of d-tubocurarine. The possible relationship of these responses to the release of histamine is discussed. The results place important limitations on the use of curare as a tool in various physiol. investigations.

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