Adrenaline enhances odorant contrast by modulating signal encoding in olfactory receptor cells

Olfactory perception is influenced by hormones. Here we report that adrenal ine can directly affect the signal encoding of olfactory receptor cells. Ap plication of adrenaline suppressed action potentials near threshold and inc reased their frequency in response to strong stimuli, resulting in a narrow er dynamic range. Under voltage-clamp conditions, adrenaline enhanced sodiu m current and reduced T-type calcium current. Because sodium current is the major component of spike generation and T-type calcium current lowers the threshold in olfactory receptor cells, the effects of adrenaline on these c urrents are consistent with the results obtained under current-clamp condit ions. Both effects involved a common cytoplasmic pathway, cAMP-dependent ph osphorylation. We suggest that adrenaline may enhance contrast in olfactory perception by this mechanism.