The effects of Zn~(2+) on the isolated superior cervical sympathetic ganglion of rabbit were stud ied with sucrese-gap method. It was found thatZn~(2+) significantly inhibited ganglienic action poten-tial with a manner of concentration-dependence.The IC-50 value was 1. 48 mmol/L. The effects ofZn~(2+) were antagonized by neostigmine and 1-cys-tein, reduced under high concentration of Ca~(2+) andenhanced under low concentration of Ca~(2+). It wasalso found that Zn~(2+) inhibited ganglionic N wave,less affected p wave and without any effect on LNwave.

Experiments were carried out on the isolatedrat phrenic nerve diaphragm preparations and chickbiventer cervicis preparations. Zn~(2+) at cumulativeconcentration inhibited muscle contractile responseto indirect stimulation without affecting the con-ductivity of nerve. The inhibiting. action of Zn~(2+) onthe muscle contractile response to indirect stimula-tion was stronger than that on contractile responseto direct stimulation. Zn~(2+) did not affect the Achsensitivity of the chick biventer cervicis muscleThe effects of Zn~(2+) on neuromuscular transmis-sion were antagonized by Ca~(2+) and L-cystein.

The effects of Cu2+ on superior cervical sympathetic ganglion of rabbits were studied by the sucrose-gap method. Cu2+ at cumula- tive concentration inhibited ganglion action potentials. IC50 of Cu2+ was 0.26 mmol/L. The effects of Cu2+ were antagonized by neostig-miae and L-cystein, while enhanced under 1/2[Ca2+] and reduced under 3[Ca2+] .Cu2+ inhibited ganglionic N wave and P wave,without affecting LN wave.