The dendron and episodic neuropeptide release.

Abstract

The unexpected observation that the long processes of gonadotrophin-releasing hormone (GnRH) neurons not only conducted action potentials, but also operated to integrate afferent information at their distal-most extent gave rise to the concept of a blended dendritic-axonal process termed the "dendron". The proximal dendrites of the GnRH neuron function in a conventional manner, receiving synaptic inputs and initiating action potentials that are critical for the surge mode of GnRH secretion. The distal dendrons are regulated by both classical synapses and volume transmission and likely operate using subthreshold electrotonic propagation into the nearby axon terminals in the median eminence. Evidence indicates that neural processing at the distal dendron is responsible for the pulsatile patterning of GnRH secretion. Although the dendron remains unique to the GnRH neuron, data show that it exists in both mice and rats and may be a common feature of mammalian species in which GnRH neuron cell bodies do not migrate into the basal hypothalamus. This review outlines the discovery and function of the dendron as a unique neuronal structure optimised to generate episodic neuronal output.