Synaptic physiology

Antagonistic regulation of synaptic vesicle priming by Tomosyn and UNC-13. McEwen, J. M. et al. Neuron 51, 303–315 (2006)

Neurotransmitter release requires the priming of synaptic vesicles by an interaction between vesicle and plasma membrane proteins to form a SNARE complex. McEwen and colleagues show that formation of the SNARE complex depends on balancing the opposite actions of two SNARE-interacting proteins: tomosyn, which inhibits SNARE complex formation, and UNC13, which promotes this process. Furthermore, they show an additional and unexpected post-priming function for UNC13 in promoting stimulus-evoked synaptic vesicle fusion.

Development

DIG-1, a novel giant protein, non-autonomously mediates maintenance of nervous system architecture. Benard, C. Y. et al. Development 133, 3329–3340 (2006)

Dedicated maintenance mechanisms that preserve the complex architecture of the nervous system once patterning is complete are now emerging. Using Caenorhabditis elegans, Benard and colleagues show that DIG1 — a giant secreted protein produced by muscle cells after the completion of development — maintains the axonal position of the ventral nerve cord and cell body positioning in ganglia of the head, probably by stabilizing the basement membrane.

Sensory systems

A second class of chemosensory receptors in the olfactory epithelium Liberles, S. D. & Buck, L. B. Nature 30 July 2006 (doi:10.1038/nature05066).

The 1,000 or so members of the odorant receptor family found on olfactory sensory neurons (OSNs) allow the discrimination of a large variety of odorants. However, some OSNs are stimulated by small peptides and pheromones, which are not ligands for odorant receptors, suggesting the presence of additional classes of receptor. A newly identified class of chemosensory receptors, expressed in a small population of OSNs that seem to lack odorant receptors, has now been described. Called trace amine-associated receptors, these receptors, which are evolutionarily conserved, appear to recognize social cues such as pheromones.

Behavioural neuroscience

Cortical 5-HT2A receptor signalling modulates anxiety-like behaviours in mice. Weisstaub, N. V. et al. Science 313, 536–540 (2006)

Altered serotonin (5-HT) signalling has been implicated in disorders of both anxiety and depression. The 5-HT2A receptor (5-HT2AR) is just one of many serotonin receptors, but its high expression level in the cortex, ventral striatum, hippocampus and amygdala — regions associated with anxiety-like behaviours — suggested that it might mediate the effects of serotonin on these behaviours. Weisstaub et al. show that mice deficient in 5-HT2AR display decreased signs of conflict anxiety, and that selective restoration of 5-HT2AR in the forebrain normalized anxiety-related behaviour. Fear and depression-related behaviours were unaffected, suggesting a specific role for cortical 5-HT2AR in modulating conflict anxiety.