Cyclic Nucleotide-Activated Currents in Cultured Olfactory Receptor Neurons of the Hawkmoth Manduca sexta

Krannich S, Stengl M. Cyclic nucleotide-activated currents in cultured olfactory receptor neurons of the hawkmoth Manduca sexta. J Neurophysiol 100: 2866-2877, 2008. First published August 6, 2008; doi: 10.1152/jn.01400.2007. Moth pheromones cause rises in intracellular Ca2+ concentrations that activate Ca2+-dependent cation channels in antennal olfactory receptor neurons. In addition, mechanisms of adaptation and sensitization depend on changes in cyclic nucleotide concentrations. Here, cyclic nucleotide-activated currents in cultured olfactory receptor neurons of the moth Manduca sexta are described, which share properties with currents through vertebrate cyclic nucleotide-gated channels. The cyclic nucleotide-activated currents of M. sexta carried Ca2+ and monovalent cations. They were directly activated by cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP), modulated by Ca2+/calmodulin, and inhibited by lanthanum. M. sexta cyclic nucleotide-activated currents developed in an all-or-none manner, which suggests that the underlying channels are coupled and act coordinately. At least one cAMP-and two cGMP-activated nonselective cation currents could be distinguished. Compared with the cAMP-activated current, both cGMP-activated currents appeared to conduct more Ca2+ and showed a stronger down-regulation by Ca2+/calmodulin-dependent negative feedback. Furthermore, both cGMP-activated currents differed in their Ca2+-dependent inhibition. Thus M. sexta olfactory receptor neurons, like vertebrate sensory neurons, appear to express nonselective cyclic nucleotide-activated cation channels with different subunit compositions. Besides the nonselective cyclic nucleotide-activated cation currents, olfactory receptor neurons express a cAMP-dependent current. This current resembled a protein kinase-modulated low-voltage activated Ca2+ current.