Isolated Neurohypophysial Terminals: Model for DepolarizationSecretion Coupling

Here we discuss the useful properties of a preparation of isolated neurosecretory nerve terminals obtained from mammalian neurohypophyses (posterior pituitaries). These nerve terminals release the two neuropeptides, oxytocin and vasopressin, which are easily assayed by radioimmunoassay and/or ELISA. Depolarization-induced exocytosis is dependent on the same parameters as those regulating release from the whole, intact neurohypophysis. The isolated nerve terminals can be identified and also imaged for intracellular Ca²⁺ and a functional synapse can be reconstituted using their purified neurosecretory granules. Furthermore, some nerve terminals are large enough to allow the use of patch-clamp techniques and the monitoring of exocytosis by capacitance and amperometric measurements. We also present evidence which show that the isolated neurohypophysial nerve terminals represent a powerful tool for studying the mechanisms underlying depolarization–secretion coupling (D-SC).