Highly read on www.cell.com in October
The number of neuron-to-neuron connections, or synapses, that an animal has is thought to vary from one time of day to another. A team of scientists at Stanford University in California set out to watch the process in live zebrafish larvae, using time-lapse fluorescence microscopy.
Lior Appelbaum, currently at Bar-Ilan University in Ramat Gan, Israel, and his colleagues followed the creation and disappearance of synapses over a 24-hour period. They focused on a particular class of neuron in two brain areas known to be involved in regulating sleeping and waking: the pineal gland and the hindbrain.
The authors showed that the number of synapses fluctuated rhythmically between day and night. They also found that a protein, Nptx2, for which levels in the brain also vary rhythmically during the 24-hour period, is involved in regulating the rhythmicity of synapse number.