Emergent Synchronous Bursting of Oxytocin Neuronal Network
(A) The top trace shows the typical intramammary pressure response indicative of a reflex milk let-down in a lactating rat; the middle trace is a raster plot indicating the corresponding spike discharge of a supraoptic neuron, and the lower trace is the corresponding firing rate record. This cell showed no burst activity preceding milk ejection, but showed a typical “post-burst” silence. (Note that the increase in intramammary pressure normally occurs about 12 s after the milk-ejection burst; this delay reflects the delay in oxytocin released from the pituitary gland reaching the mammary gland, not a delay in oxytocin release). (B) Simultaneous activity of two cells in the model, in one of which the sensitivity to oxytocin has been disabled. While the upper cell shows typical intermittent bursts, the lower cell shows post-burst silences, but no bursts, due to removal of afferent excitation by oxytocin.