Patch-clamp analysis of peptidergic excitation in rat supraoptic neurons

The magnocellular neurosecretory cells (MNCs) synthesizing and secreting the hormones vasopressin (VP) and oxytocin (OXT) are best known for their direct role in controlling the body fluid homeostasis through changing their firing rates in response to changes in the osmolarity of the extracellular fluid, and subsequent neurohypophysial hormone release. In response to dehydration, MNCs fire clusters of action potentials to maintain sustained high levels of VP to overcome the circulatory failure (Poulain et aL, 1988). Changes in the osmotic pressure have been shown ta be a potent regulater of MNC activity and neurohypophysial hormone release. In addition, recent eleetrophysiological studies have shown that different substances released in the central nervous system (CNS) such as catecholamines and neuropeptides can modulate the excitability of MNCs and play a role in their hormone release into the circulation