Caffeine contractures in denervated frog muscle |
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| Authors: | B. A. Kotsias R. A. Venosa P. Horowicz |
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| Affiliation: | (1) Department of Physiology, University of Rochester, School of Medicine and Dentistry, 601 Elmwood Avenue, 14642 Rochester, New York, USA;(2) Present address: Instituto de Investigaciones Medicas, Donato Alvarez 3150, RA-1427 Buenos Aires, Argentina;(3) Present address: Catedra de Fisiologia, Facultad de Medicina, 60 y 120, RA-1900 La Plata, Argentina |
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| Abstract: | Caffeine contracture tension, effect of caffeine on the resting membrane potential, and caffeine influx in normal and denervated frog sartorius muscle have been investigated. Peak caffeine contracture tension is increased after denervation at all caffeine concentrations. The percentage increases in tension are highest for lower caffeine concentrations. The caffeine concentration required for half maximum tension is decreased from about 3.6 mM in control muscles to 2.6 mM in denervated muscles. Caffeine at 3.5 mM produces a depolarization of about 6 mV in control muscles and 16 mV in denervated muscles. The large contracture tensions observed in denervated muscles are not due to the greater depolarization produced by the drug in denervated muscles since innervated muscles depolarized to the same level by external K+ do not enhance caffeine contracture tension. Both control and denervated muscles are highly permeable to caffeine. The increases in sarcoplasmic reticulum development (Moscatello et al. 1965) and calcium content (Picken and Kirby 1976) promoted by denervation may explain the larger tension elicited by caffeine in denervated muscles. |
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| Keywords: | Frog muscle denervation Caffeine contractures Resting potential Caffeine influx |
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