Cyclic nucleotide-activated currents in cultured olfactory receptor neurons of the hawkmoth Manduca sexta.
Moth pheromones cause rises in intracellular Ca(2+) concentrations that activate Ca(2+)-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 Ca(2+) and monovalent cations. They were directly activated by cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP), modulated by Ca(2+)/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 Ca(2+) and showed a stronger down-regulation by Ca(2+)/calmodulin-dependent negative feedback. Furthermore, both cGMP-activated currents differed in their Ca(2+)-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 Ca(2+) current.
Krannich
Steffi
S
Biology, Animal Physiology, Philipps-University of Marburg, Karl-von-Frisch-Strabetae, Marburg D-35032, Germany.
Stengl
Monika
M
D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology; D000200:Action Potentials / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002478:Cells, Cultured; D006152:Cyclic GMP / Q000031:analogs & derivatives / Q000494:pharmacology; D004307:Dose-Response Relationship, Radiation; D004558:Electric Stimulation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D007811:Lanthanum / Q000494:pharmacology; D018402:Manduca / Q000033:anatomy & histology*; D008564:Membrane Potentials / Q000187:drug effects* / Q000502:physiology; D009532:Nickel / Q000494:pharmacology; D009712:Nucleotides, Cyclic / Q000494:pharmacology*; D009833:Olfactory Pathways / Q000166:cytology*; D018034:Olfactory Receptor Neurons / Q000187:drug effects*; D018408:Patch-Clamp Techniques / Q000379:methods; D013449:Sulfonamides / Q000494:pharmacology; D015032:Zinc / Q000494:pharmacology
D004791:Enzyme Inhibitors; D009712:Nucleotides, Cyclic; D013449:Sulfonamides; D015124:8-Bromo Cyclic Adenosine Monophosphate; C016276:8-bromocyclic GMP; C017967:W 7; D007811:Lanthanum; D009532:Nickel; D006152:Cyclic GMP; D015032:Zinc; D002118:Calcium