Inhibitory effects of exogenously applied met-enkephalin on submandibular ganglion cells

In this study, effects of exogenously applied Met-enkephalin on hamster submandibular ganglion cells were investigated using an intracellular recording technique. Met-enkephalin (10 microM) was applied to cells by pressure ejection (2 kg/cm2, 50 msec) from a micropipette. More than 30% of the cells caused a hyperpolarization (amplitude: about 3 mV) accompanied by an increase in potassium conductance. After 30-40 ejections, the Ca2+ spike was shortened by 18.1%, and the nicotinic transmission was depressed. The inhibitory effect on presynaptic terminals was blocked by naloxone (10 microM).