SINGLE UNIT ACTIVITY AND MECHANOGRAM OF THE COCCYGEAL LYMPH-HEART OF TOAD

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Abstract
A method is described for the isolation and extracellular recording of single unit activity from the coccygeal lymph-heart of toad in spontaneous activity. The single unit activity produced by an individual systole of the organ was composed of 3 to 5, most frequently, of 4 simple components, which were slow junctional potentials (s.j.p.) in nature, successively superimposing on preceding ones, but without initiating any muscle impulse. The junctional potential which was produced by stimulation to the root, was analogous to the intracellular record obtained in the previous report, and also similar to s.j.p. in the skeletal muscle. Conduction rate was determined on the nerve fibers which were responsible for the single unit activity. At the level of the XIth ventral root, the rates ranged from 6 to 14 m /second which might fall between those of the large- and small-nerve fibers in the skeletal muscle. Mechanogram of the systoles of the organ was recorded with a calibrated mechano-transducer, simultaneously with the electrical activity. Each of the systoles showed a dome-like configuration of about 0.5 second and 0.3 second in duration at the levels of 10% and 50% of their maximum height. Complete relaxation took about 0.3 second after cessation of nerve volleys. These findings were discussed especially in terms of the properties of the slow-muscle system in skeletal musculature in toad.

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