Experience-dependent activation of extracellular signal-related kinase (ERK) in the olfactory bulb

Abstract Protein kinase‐mediated signaling cascades play a fundamental role in translating extracellular signals into cellular responses in CNS neurons. The mitogen‐activated protein kinase / extracellular signal‐regulated kinase (MAPK/ERK) pathway participates in regulating diverse neuronal processes such as proliferation, differentiation, survival, synaptic efficacy, and long‐term potentiation by inducing cAMP‐response element (CRE)‐mediated gene transcription. Central olfactory structures show plasticity throughout the lifespan, but the role of the MAPK/ERK pathway in odor‐evoked activity has yet to be determined. Therefore, we examined the effect of odorant exposure and early postnatal deprivation on ERK activity. We found that odor stimulation induced ERK phosphorylation, that activation of the ERK pathway was decreased with early postnatal deprivation, and that ERK phosphorylation was subsequently increased by restoring stimulation. Further, locations of ERK activation in bulbar neurons after exposure to single odorants corresponded to odor‐evoked activity patterns found with other measures of activity in the bulb. Finally, due to the cytoplasmic location of pERK, activated dendrites belonging to the primary excitatory output neurons of the bulb were observed following a single odor exposure. The results indicate that the MAPK/ERK pathway is activated by odorant stimulation and may play an important role in developmental sensory plasticity in the olfactory bulb. J. Comp. Neurol. 479:234–241, 2004. © 2004 Wiley‐Liss, Inc.