Synaptic activity regulates gene transcription in neurons. The coupling between synaptic transmission and transcription is accomplished by the second messenger calcium, which enters the cell through synaptic receptors and voltage-gated calcium channels and binds enzymes that activate transcription factors. In schematic diagrams showing these calcium-activated pathways, synaptic calcium influx happens conveniently close to the nucleus (West et al. 2001). In reality, however, synapses are distributed over an extensive dendritic tree. How then is information about synaptic activity passed on to the nucleus, which can be hundreds of micrometres from activated synapses? Passive diffusion is too slow for a long-range signalling system, especially given the high buffer capacity of the dendritic cytoplasm for calcium and the slow diffusion of these buffers (Helmchen et al. 1996). The report of Nakamura et al. (2002) in this issue of The Journal of Physiology takes a closer look at the properties of regenerative calcium waves in the apical dendrite of CA1 pyramidal cells (see also: Kapur et al. 2001; Nakamura et al. 1999, 2000). These waves, which depend upon activation of inositol 1,4,5-trisphosphate (IP3) receptors, are a prime candidate for a signalling system that locally integrates synaptic activity in the dendrite and sends a binary signal to the nucleus (Berridge, 1998).