CALCIUM CONTROLS 2ND-MESSENGER SIGNALING IN OLFACTORY CILIA

The increase in intracellular calcium concentration elicited by odoran t stimulation seems to be involved in down-regulating the responsivene ss of olfactory neurons to subsequent stimuli. The present study sugge sts that this regulatory effect may be due to a calcium-dependent atte nuation of the olfactory signalling cascade; the odor-induced cyclic a denosine monophosphate (cAMP) response in olfactory cilia is diminishe d by calcium in a dose-dependent manner. This reduced cAMP signal is n ot due to an activation of phosphodiesterases by elevated calcium leve ls, but rather seems to be mediated by the inhibition of adenylate cyc lase by calcium ions.