The depressing effect of tetracaine and ryanodine on the slow outward current correlated with that of contraction in voltage-clamped frog muscle fibres
✍ Scribed by Mohammad Nasri-Sebdani; Flavien Traoré; Christian Cognard; Daniel Potreau; Jean -Pierre Poindessault; Guy Raymond
- Publisher
- Springer
- Year
- 1990
- Tongue
- English
- Weight
- 687 KB
- Volume
- 416
- Category
- Article
- ISSN
- 0031-6768
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✦ Synopsis
The effects of tetracaine (10-50 laM) and ryanodine (0.1 -10 gM) were tested on the slow outward K + current (Iso) and the mechanical tension of isolated frog muscle fibres in a voltage-clamp device (double mannitol-gap) connected to a mechanoelectric transducer. In the concentration range tested, both drugs induced a simultaneous inhibition of tension and current. In all cases the effect on tension was twice that on current. The tetracaine-induced current and tension blocks were fully reversible and dose-dependent. In contrast the ryanodine effects on current and tension were not reversible and did not exhibit a dose dependence except for the delay before the onset of the response, which was shortened when the concentration was raised. Linear regression analysis of the time-dependent and dose-dependent effects of both drugs indicated a strong correlation between the decreases in tension and current. It is concluded that the slow outward current is partly under the control of the Ca z+ release from sarcoplasmic reticulum during contraction.