The outgrowth of oligodendrocyte cell processes is vital for the formation of myelin, but the underlying mechanisms are not well understood. Kim, DiBernardo and colleagues now take us a step closer to understanding these mechanisms with the discovery that a WAVE (Wiskott–Aldrich syndrome protein family verprolin homologous) protein is essential for the morphological development of oligodendrocytes and consequent myelin formation through its influence on cytoskeleton dynamics.

It is well accepted that retinoic acid (RA) is important for a range of processes during maturation of the nervous system, including early development of the eye. Sen and colleagues now show that RA is also required for later dorsoventral patterning of the chick retina and highlight the mechanisms of action of RA in this process.

Stimulation of excitatory neurons triggers the movement of calcium into dendritic spines and the build up of second messengers in the spine head, which, in turn, activates regulatory signalling cascades that underpin alterations in the strength of excitatory synapses. The level of signalling molecules in the spine head is therefore crucial for the induction of synaptic plasticity, and Bloodgood and Sabatini have now shown that the spine neck has a dynamic role as a diffusion barrier in regulating the movement of these molecules into and out of the spine head.

Keeping Trk of painA new study by Fang et al. describes the sensory properties of nociceptors that express TrkA in the dorsal root ganglion (DRG), and provides important evidence that links TrkA expression to the electrophysiological properties of certain nociceptors.Combining immunocytochemical and electrophysiological techniques, the authors showed that in the rat DRG, TrkA was highly expressed only in nociceptive neurons, although there was weak TrkA expression in some low-threshold mechanoreceptors.More over, this high intensity of expression was present in the oftenoverlooked fast-conducting (Aα/β), as well as slow-conducting (C and Aδ), types of nociceptor.These researchers therefore investigated whether the high levels of TrkA expression in nociceptors of the DRG might explain the strong effect of nerve growth factor (NGF) on these neurons.Their studies revealed that the level of TrkA expression in individual Aα/β nociceptors correlated with electrophysiological properties that are characteristic of nociceptors, including slow conduction velo city, long action potential and afterhyperpolarization durations and large action potential amplitudes.This correlation did not hold for C and Aδ nociceptors, in which TrkA is also highly expressed.Previous studies have reported that NGF influences the expression of the sodium channel Nav1.8 in DRG neurons.This raises the interesting possibility that the link between TrkA www.