Formation of precise connections in the olfactory bulb occurs in the absence of odorant-evoked neuronal activity

Olfactory neurons expressing the-same odorant receptor converge to a small number of glomeruli in the olfactory bulb. In turn, mitral and tufted cells receive and relay this information to higher cortical regions. In other se nsory systems, correlated neuronal activity is thought to refine synaptic c onnections during development. We asked whether the pattern of connections between olfactory sensory axons and mitral cell dendrites is affected when odor-evoked signaling is eliminated in mice lacking functional olfactory cy clic nucleotide-gated (CNG) channels. We demonstrate that olfactory sensory axons converge normally in the CNG channel mutant background. We further s how that the pruning of mitral cell dendrites, although slowed during devel opment, is ultimately unperturbed in mutant animals. Thus, the olfactory CN G channel-and by inference correlated neural activity-is not required for g enerating synaptic specificity in the olfactory bulb.