AbstractThe effects of pindolol and sotalol on neuromuscular transmission were tested using intracellular micro‐electrode recording of resting membrane potentials, miniature end‐plate potentials and end‐plate potentials, and recording of muscle contractions upon nerve stimulation of rat phrenic nerve‐hemidiaphragm preparations. Both pindolol and sotalol reduced the amplitudes of miniature end‐plate potentials and end‐plate potentials in a dose‐dependent manner without significantly affecting their time‐courses. Pindolol, but not sotalol, also increased the frequency of the miniature end‐plate potentials and decreased the number of acetylcholine quanta released by nerve impulses. Neither of the drugs significantly affected resting membrane potentials of the muscle fibres or excitability of the motor nerve to ele