[Neuromuscular effects of vecuronium d-tubocurarine and succinylcholine in malnourished rat's diaphragm].

The pharmacodynamics of neuromuscular blocking agents in malnutrition have not been well delineated. In the present study, the neuromuscular effects of vecuronium (Vb), d-tubocurarine (d-Tc) and succinylcholine (SCh) in malnutrition were investigated. Male Sprague-Dawley rats aged 7 weeks were divided into malnourished and control groups. One fifth of their usual daily consumption was allowed in the malnourished group for 10 days. The animals were anesthetized and phrenic nerve-hemidiaphragm preparations were dissected. The preparations were placed in an organ bath containing oxygenated Krebs' solution at 37 degrees C. The diaphragms were stimulated through their phrenic nerves with supramaximal stimuli of 0.2 msec at the rate of 0.1 Hz. The responses were measured by an isometric transducer. The 50% and 90% inhibitory concentrations (IC50, IC90) of Vb, d-Tc and SCh were determined form dose-response curves. Body weight was significantly lower in malnourished group than in the control group. IC50 and IC90 of both Vb and d-Tc were significantly higher in the malnourished group than in the control group (P < 0.001). However, IC50 and IC90 of SCh were significantly lower in the malnourished group than in the control group (P < 0.0001). In this study, malnutrition increased resistance to nondepolarizing neuromuscular blocking agent and sensitivity to SCh compared with the control. These results suggest that malnutrition might induce similar changes of acetylcholine receptor which are observed in denervation or burn injury.