Morphological Studies of Dendrites and Dendritic Secretion

Abstract

This review attempts to highlight the role that morphological studies have played in developing our understanding of the importance of secretion from dendrites. It is now clear that dendritic secretion plays a role in the regulation of dendritic morphology; whether during development or in the morphological plasticity that accompanies both synaptic-induced activity and physiological states such as lactation. Dendrites of petidergic neurons often contain substantial amounts of vesicle-packaged peptide and, in the magnocellular neurosecretory system and suprachiasmatic nucleus at least, the densecored vesicles can be secreted to exert autocrine and paracrine effects on both the magnocellular neurons and their afferent synaptic input. Whether these or other soluble peptides can also be secreted from dendrites via small electron-lucent vesicles and the constitutive route remains to be determined. Finally, dendritic secretion plays a role in the insertion of receptor proteins into the postsynaptic membranes and thus controls the local receptive properties of the neurons. The extent to which all these functions are controlled very locally to produce functional microdomains in the very simple or very elaborately branched dendritic trees is an important question for the future.