Failure to implicate camp in transduction in lobster olfactory receptor cells

The possible role of adenosine 3',5'-cyclic monophosphate (cAMP) in olfactory transduction in the spiny lobster was investigated using radioimmunoassay of cAMP and intracellular recording. Application of forskolin or 1-isobutyl-3-methylxanthine increased cAMP levels in intact sensilla containing the chemoreceptive outer dendritic segments of the lobster olfactory receptor cell, thereby demonstrating adenylate cyclase and phosphodiesterase activity in the sensilla. A complex odor mixture and identified excitatory odor molecules failed to stimulate the production of cAMP, however In intracellular recordings, superfusion of the outer dendritic segments with forskolin, 1-isobutyl-3-methylxanthine and cyclic nucleotide analogs had no direct effect on odor-responsive cells. These compounds did cause infrequent enhancements (six of 42 cells) of odor-evoked receptor potentials, but processes other than transduction are the most likely causes of this effect. We conclude that cAMP-dependent transduction mechanisms are unlikely to mediate most odor responses in lobsters, in contrast to transduction mechanisms in amphibians and rats.