Regulation of Olfactory Signalling via cGMP‐Dependent Protein Kinase

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Abstract
Strong odor stimuli elicit a slow and sustained increase of the cGMP concentration in isolated rat olfactory cilia. Elevated cGMP levels appear to attenuate the primary response to odorant stimulation. Incubating cilia with membrane‐permeable cGMP derivates caused a significantly reduced cAMP signal in response to odorant stimulation. This inhibitory effect was mimicked by 8‐(4‐chlorophenlythio)‐cGMP, a selective activator of cGMP‐activated protein kinases; in contrast, a selective inhibitor, [8‐(4‐chlorophenylthio)‐guanosine‐3′,5′‐cyclic monophosphorothioate] of cGMP kinases enhanced the reactivity to odorant stimulation. The data suggest that the responsiveness of olfactory sensory cells is governed by a cGMP‐dependent protein kinase. Western‐blot analysis using subtype‐specific antibodies indicated that cytosolic type‐I cGMP kinase, but not the membrane‐associated type‐II cGMP kinase, is expressed in olfactory sensory neurons.