Hippocampal neurons were prepared from 17 d old NMRI mice and grown as described previously (G. Grosse et al., (2000) J. Neurosci. 20: 1869-1882). The figure shows the distribution of neuronal calcium sensor-1 (NCS-1) (red) and synaptobrevin (green) in hippo-campal cell cultures after 19 d in vitro. Numer-ous synapses immunoreactive for synaptobrevin also show NCS-1 immunoreactivity. NCS-1 derived from invertebrate homologs has been referred to as frequenin.