Figure 3.

Models of spinule functions. a, Process whereby trans-endocytosis of spinules removes excess presynaptic and postsynaptic plasma membrane after substantial activation results in transient perforated or segmented synapses on mushroom spines. This process could also provide retrograde signaling. b, Neighboring axons vying for synapses via spinules on the necks and heads of thin spines. c, Intercellular signaling between thin spines and perisynaptic glia via spinules. Reproduced from ref. 76 with the permission of the Society of Neuroscience (copyright 2004) and Dr. Harris.