Technical Reports in 2010

Dombeck and colleagues describe a method for two-photon calcium imaging using a genetically encoded indicator in the hippocampus of awake, behaving mice. This powerful approach permits the recording of multiple hippocampal place cells' activity with subcellular resolution as the mice run on a track in a virtual reality environment.

This paper reports the development of a K⁺-selective glutamate receptor, HyLighter, that reversibly inhibits neuronal activity in response to light. The low light requirement and bi-stability of HyLighter could be useful for studying neural circuitry.

Dieterich et al. describe a methodology to label all newly synthesized neuronal proteins in situ. This method, which they name FUNCAT, relies on the inclusion of noncanonical amino acids and selective fluorescent labeling via click chemistry. The authors show that this system is amenable to dual pulse-chase experiments and dynamic tracking of newly synthesized proteins.

Understanding the role of astrocytic calcium signals has been hindered by our inability to measure calcium in small volume compartments. Here, the authors develop a technique to do this by modifying the genetically encoded calcium sensor GCaMP2 to ensure greater expression near the membrane.

The authors devised a method for detecting the bioluminescent Ca²⁺ sensor GFP-Aequorin in freely behaving zebrafish larvae. To demonstrate the efficacy of the technique, they targeted the sensor to a genetically specified population of hypothalamic neurons. The resulting neuroluminescence reveals patterns of neuronal activity that are associated with distinct swimming behaviors.

This paper reports the first recording from brain neurons of flying Drosophila. The responses of visual interneurons to moving grate stimuli were substantially modulated by flight, as compared with the resting situation.

Channelrhodopsins such as ChR2 can drive spiking with millisecond precision. However, when ChR2 is highly expressed, a single light pulse can produce extra spikes, and ChR2 does not allow sustained spike trains above about 40 Hz. Rapid ChR2-driven spike trains can also cause plateau potentials. Here, the authors report an engineered opsin gene, ChETA, that overcomes these limitations and allows sustained spike trains up to 200 Hz.