Tripping the HCN breaker.

Hyperpolarization-activated cyclic nucleotide-gated (HCN) channels regulate neuronal excitability, pacemaking, dendritic integration, and homeostatic plasticity and are culprits in aberrant neuronal activity in certain epilepsies. In this issue of Neuron two manuscripts (Santoro et al. and Zolles et al.) report that HCN channel gating and expression are controlled by Trip8b (Pex5R) but with a bidirectional spin.