Oscillation in resting tension of chick skeletal muscle treated with toxin V from scorpion venom, reduced [calcium]o and cadmium.

1. An oscillation in resting tension of the chick biventer cervicis muscle is induced by scorpion toxin (CsT-V), reduced [Ca]o and by Cd2+. Other chick muscles, e.g. semispinalis cervicis, anterior and posterior latissimus dorsi, also oscillate with the same treatments. The period of the oscillation in the biventer cervicis muscle is uniform, averaging 5-6 min. 2. The oscillation and the period are very sensitive to changes in temperature, [Ca]o, [K]o, ouabain and tetrodotoxin [TTX]. The oscillation is resistant to twitch blocking dosages of nicotinic antagonists. 3. The period of the oscillation varies inversely as the temperature (26-37 degrees C), log [K]o and [ouabain] and directly as the log [Ca]o and [TTX]. 4. These data support the inference that the oscillator is postjunctional and results from fluctuation in the electrochemical gradient of ions across the muscle cell membrane. The role, if any, of the Na+, K+ pump in the primary oscillogenic mechanism is not evident from our data.