• A T Melton, J F Antognini, and G A Gronert.
• Department of Anesthesiology, University of California, Davis, USA.
• Acta Anaesthesiol Scand. 1999 Aug 1; 43 (7): 764-9.

BackgroundSkinned fibers from normal human masseter muscle have greater caffeine and calcium sensitivity than skinned fibers from vastus muscle. We examined sensitivity to caffeine and halothane in fresh, cut muscle bundles (non-skinned) from human masseter muscle.MethodsMasseter bundles (caffeine, n=25, halothane, n=19) excised from 10 humans under general anesthesia had tension measured in 37 degrees C baths during the addition of caffeine (0.5, 1, 2, 4, 8, 32 mM) or 3% halothane. Results were compared to those of our previous studies (1989, 1997, 25 patients) of vastus bundles (caffeine, n=71, halothane, n=63) using the same protocol, technicians, and equipment.ResultsBaseline force in the caffeine test was 2.10+/-1.57 for masseter, and 2.02+/-1.68 and 1.82+/-1.29 respectively for vastus muscle. Force at 32 mM caffeine concentration was 11.2+/-9.9 g for masseter, 11.0+/-5.4 and 13.5+/-7.5 g for vastus. Concentration-response curves were virtually identical. In the halothane group, neither baseline values (masseter 1.47+/-1.30, vastus 1.91+/-1.32 and 2.15+/-1.71) nor contractures in response to 3% halothane were different. Most bundles had no contracture in response to 3% halothane; 3 masseter bundles and 2 vastus bundles (1989) developed contractures of less than 0.05 g. Three vastus bundles (1997) developed contractures >0.2 g.ConclusionContracture responses of intact cut masseter and vastus bundles (non-skinned) do not differ with respect to caffeine and halothane. Responses of skinned fibers might demonstrate greater sensitivity under certain conditions, but they do not reflect those of intact cut bundles.

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