Electrical activity and secretion in salivary gland cells of the leech, Oosthuizobdella garoui (Hirudinea: rhynchobdellida)

Abstract

1. Each salivary gland cell of Oosthuizobdella extends a single process (ductule) anteriorly into the proboscis. Secretion occurs at the ductule ending. 2. The cells produce calcium-dependent action potentials, accompanied by secretion, in response to stimulation of the stomatogastric nerve or to addition of 5-hydroxytryptamine (10 −4 M), ethanol (4–8%) or calcium-free saline. 3. Activation of gland cells by the nervous system or by 5-HT occurs near the ductule ending, and impulses are conducted along the ductule to the cell body. 5-HT is possibly the neuroglandular transmitter. 4. Acetylcholine (10 −4M) transiently excites the gland cell body and increases the amplitude of action potentials. Dopamine and octopamine (10 −4 M) do not elicit action potentials, but dopamine increases cell excitability. These substances do not initiate secretion. 5. The gland cells function independently: there is no electrical or dye coupling. 6. Secretion can be monitored visually from individual cells. This presents the possibility of studying excitation-secretion coupling in a single cell.