How synaptic strength is distributed along a motor neuron and its branches is still a not well understood item. Guerrero et al. (Heterogeneity in synaptic transmission along a Drosophila larval motor axon. Nature Neuroscience 8, 1188-1196, 2005) to address the question of how transmission strength is distributed among the many axon’s collaterals making junctions with muscular cells, created synapcam, a version of the Ca2+ reporter cameleon.

Synapcam can detect Ca2+ influx through post-synaptic glutamate receptor with single-impulse and single-bouton resolution. The authors combined this approach with pre-synaptic imaging, so obtaining the following results:


1) transmission strength is determined mainly presynaptically

2) transmission strength vary in a gradient along the length of axonal branches

3) distant connections make stronger functional associations.


BM&L-November 2005