FORSKOLIN ENHANCED OFF-RESPONSE IN THE TURTLE OLFACTORY SYSTEM

Olfactory responses appear not only at the onset of odor stimulation, but also at the termination of the stimulation. It is widely considere d that the cAMP-pathway is involved in the generation of odor response s. We examined how cAMP affects the generation of off-responses. To ex plore the role of the cAMP-pathway, odorants were applied to the turtl e olfactory epithelium after forskolin al high concentrations which sa turated the olfactory response to forskolin. Various odorants induced off-responses after 50 mu M forskolin, indicating that off-responses a re not induced via the cAMP-dependent pathway. However, the magnitude of the off-response after forskolin varied from 100 to 1400% of those of off-responses in its absence, indicating that forskolin greatly enh anced the off-responses to some odorants. The off-response after 0.1 m M citralva was also enhanced by 3 mM 8-(4-chlorophenylthio)-adenosine 3',5'-cyclic monophosphate (cpt-cAMP). These results suggested that cA MP modulates off-responses in the turtle olfactory system.