“…It was found that L-arginine, but not D-arginine, produced facilitation of neurotransmission at 5 Hz and fade of transmission at 50 Hz and that N G -nitro-L-arginine (NOARG) antagonized both the facilitatory and inhibitory effects of L-arginine which suggested that NO may modulate the release of ACh from the motor nerve terminals (Queiroz and Alves-Do-Prado, 2001). Since the role of calcium (Endo, 1985) and NO (Ambiel and Alves-Do-Prado, 2001;Queiroz and Alves-Do-Prado, 2001) in the neuromuscular transmission has already been established, the possible involvement of calcium and NO in the mode of action of the active principle of black tea on rat diaphragm was also investigated in the study.…”