Frequency-dependent depletion of secretory vesicle pools modulates bursting in vasopressin neurones of the rat supraoptic nucleus

When stimulated, vasopressin neurones discharge lengthy, repeating bursts of action potentials. An increase in the stimulus strength causes both a lengthening of the bursts' active phase and an increase in the intra-burst firing frequency. Here we extend our earlier model (P. Roper, J. Callaway, W. Armstrong. J. Neurosci. 24(20) (2004) 4831.) for phasic bursting at a constant stimulus. We show that an increase in burst length could be due to a reduction of the co-secretion of an inhibitory factor, dynorphin, and we propose this to be caused by a frequency-dependent depletion of the pool of secretory vesicles.