1. Probing Repetitive Firing in Pyramidal Neurons
Steven A. Prescott, Stéphanie Ratté, Yves De Koninck, and Terrence J. Sejnowski

In response to a continuous stimulus, some neurons slow their firing rate, an adaptation process that is mediated by slow, voltage-dependent potassium channels such as I_M and I_AHP. This week, Prescott et al. show that adaptation can be modulated by membrane conductance, or shunting, as occurs with background synaptic activity. In experiments and simulations, adaptation was sufficient to interrupt firing in CA1 pyramidal neurons when membrane conductance was high, but firing persisted when conductance was low. According to their model, shunting, by increasing the voltage threshold for spike generation, also enhances subthreshold activation of I_M, which in turn abolishes repetitive firing. Because adaptation can minimize background spiking, the nonlinear interaction between shunting and adaptation can make for a more precise neuronal response at low firing rates by acting like a coincidence detector rather than an integrator.

2. A Well-Rounded View of the Fly Synapse
Natasha M. Viquez, Caroline R. Li, Yogesh P. Wairkar, and Aaron DiAntonio

Fly fishing in St. Louis can be quite interesting it appears. This week, Viquez et al. went fishing for regulators of the Drosophila neuromuscular junction (NMJ) and pulled out a subunit of protein phosphatase 2A (PP2A), a serine threonine phosphatase required for many cellular processes. The authors generated >2500 transposable P-element insertion lines in which the yeast upstream activating sequence promoter was randomly inserted into the fly genome. After selecting lines with altered synapse morphology, they identified four in which the P-element insertion was positioned to overexpress the gene encoding the regulatory B′ subunit of PP2A. Null mutants of the gen
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Contact: Sara Harris
sharris@sfn.org
202-962-4000
Society for Neuroscience
5-Sep-2006