The effects of ketamine on the muscle cell membrane and intracellular Ca++ stores were investigated in vitro. Wistar rats (200-230 g) were studied. After decapitation, hemidiaphragma nerve-muscle preparations were placed in an isolated organ bath with Krebs solution (pH=7.4) in which insuflated with oxygen (95 %) and carbon dioxide (5 %) gas mixture. The following experiments were performed: A. 10 nerve-muscle preparations were used for bioelectrical recordings. Preparation was placed in a bath with a capacity of 10 mL and insufflation facilities. Micro electrodes were inserted intramuscularly and membrane potentials and action potentials via the stimulation of nerve recorded with the ketamine concentrations of 30, 50, 70, 90, 100 and 120 µM/L Amplitude, latans and overshoot parameters were calculated from the recorded curves. B. 13 nerve-muscle preparations which were inserted between the platin electrodes were stimulated directly or indirectly with supramaximal electrical stimuli (0.2 ms duration and 0.05 Hz) for biomechanical recordings. After normal strength of muscles were recorded ketamine was added into the bath to obtain the concentration of 21, 31.6, 42, 52.6, 63 and 73.6 µM/L and records were taken. The contraction changes were evaluated. Action potential wets observed to be begun without muscle contraction with the concentration of 73.6 µM/L of ketamine. This result may show that ketamine blocks not only the Na+ channels but also sarcoplasmic Ca++ channels. On, the other hand unchanging contracture stressed that ketamine does not effect on Ca++ reuptake
