Induction of apoptosis in mouse [correction of rat] olfactory neuroepithelium by synaptic target ablation.

The olfactory system provides a useful in vivo model for studying the influence of synaptic targets on the survival of relay neurones. The bipolar sensory neurones located in the olfactory mucosa project synaptically onto the ipsilateral olfactory bulb, and their survival depends on the integrity of this connection. We demonstrate here that the retrograde neuronal degeneration induced by olfactory bulb removal involves apoptosis. As revealed by typical nucleosome-sized fragmentations of the genomic DNA, the apoptosis rate reaches a maximum 32 h after bulbectomy. A transient c-fos mRNA accumulation was detected, peaking 16 h after bulbectomy, suggesting that c-fos is involved in the early steps of programmed cell death.