| Abstract: | Neurosecretory granule exocytosis from axon terminals in the crayfish (Orconectes virilis) sinus gland can be effected by alterations in intracellular ionic concentrations through modification of the bathing medium or by electrical stimulation. This may result in increased numbers of exocytotic profiles involving one granule (single exocytosis) or several granules (compound exocytosis), which we interpret as evidence of stimulated neurosecretion. Our results suggest that increased free intracellular Ca++ together with a decrease in intracellular K+ are prerequisite for and sufficient to elicit increased exocytosis from sinus gland terminals. Similar release, stimulated by horseradish peroxidase, indicates that local surface permeability changes are involved. A minor response to high-K+-Ringer, and secretion via compound exocytosis, are uncharacteristic of cells with a neural ancestry. |
