Counter effects of higenamine and coryneine, components of aconite root, on acetylcholine release from motor nerve terminal in mice.

The counter effects of higenamine and coryneine, components of aconite root, on acetylcholine (ACh) release from motor nerve terminals in the mouse phrenic nerve-diaphragm muscle preparation were studied by a radioisotope method. Both nerve-evoked release and spontaneous release of [3H]-ACh from the preparation preloaded with [3H]-choline were measured. The change in the tetanic tension of muscle was simultaneously recorded in the same preparation. Higenamine (10 microM) augmented both the nerve-evoked and spontaneous ACh releases, and the muscle tension. The effects were inhibited by pretreatment with propranolol (10 microM), a beta-adrenoceptor antagonist. Coryneine reduced the nerve-evoked release of ACh, accelerated the decay of tetanic tension (tetanic fade) at 30 microM, and it depressed the peak amplitude of tetanic tension at a higher concentration of 100 microM. These results suggest that of the two components contained in aconite root, higenamine increases ACh release via activation of beta-adrenoceptor, and conversely coryneine depresses ACh release by preferentially acting at motor nerve terminal.