A plastic clock

Abstract

Although circadian clocks normally run with a 24 hr period, Brancaccio et al. (2013) report in this issue of Neuron that transiently activating G protein signaling can lengthen period even after the stimulus is removed, revealing an unexpected plasticity in the central brain clock.

Figure 1. A Model for G Protein Signaling in the SCN

In this simplified model, VIP-expressing clock neurons in the SCN receive inputs via Gq, which increases intracellular Ca²⁺ levels and modifies clock gene oscillations that, in turn, determine the timing of VIP release. VPAC2, the VIP receptor, activates Gs signaling in SCN neurons that do not express VIP and this alters clock gene oscillations in these downstream clock neurons.