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

CT ED P RO O Abstract 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. r 2004 Published by Elsevier B.V.