title: Cyclic nucleotide-gated channels are involved in phototransduction of dermal photoreceptors in Lymnaea stagnalis.
abstract: Dermal photoreceptors in the pond snail Lymnaea stagnalis mediate the whole-body withdrawal response, including pneumostome closure, elicited by a shadow passing over the pneumostome area. The pneumostome closure response is part of the defense reaction in Lymnaea. The shadow or 'light-off' stimulus elicits activity in a higher order interneuron, RPeD11, which has a major role in mediating defensive withdrawal behavior elicited by noxious or threatening stimuli. Here, we tested our hypothesis that cyclic nucleotide-gated (CNG) channels are involved in the dermal photoreceptor-mediated transduction of the shadow stimulus. The response to the shadow stimulus recorded in RPeD11 was abolished by 500 μM cis-diltiazem, which blocks cGMP-activated conductance of CNG channels. On the other hand, the shadow response elicited in RPeD11 was not blocked by 2-amino ethyldiphenyl borate (2-APB), a transient receptor potential (TRP) channel blocker. Consistent with the electrophysiologic data, cis-diltiazem blocked the shadow-evoked withdrawal response, whereas 2-APB did not block the withdrawal response evoked by the shadow stimulus in intact freely behaving Lymnaea. Together, these findings support the hypothesis that the second messenger in dermal photoreceptors involves CNG and not TRP channels.
authors.affiliation: Ecology, Evolution and Marine Biology, University of California Santa Barbara, Santa Barbara, CA 93106-6110, USA.
authors.forename: Sabrina
authors.initials: S
authors.lastname: Pankey
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Sunada
authors.forename: Tetsuro
authors.initials: T
authors.lastname: Horikoshi
authors.forename: Manabu
authors.initials: M
authors.lastname: Sakakibara
mesh_terms: D000818:Animals; D001896:Boron Compounds / Q000494:pharmacology; D006152:Cyclic GMP / Q000494:pharmacology; D054815:Cyclic Nucleotide-Gated Cation Channels / Q000502:physiology*; D004110:Diltiazem / Q000494:pharmacology; D007395:Interneurons / Q000187:drug effects / Q000502:physiology; D055537:Light Signal Transduction / Q000502:physiology*; D008195:Lymnaea / Q000502:physiology; D010775:Photic Stimulation; D010786:Photoreceptor Cells / Q000502:physiology; D012879:Skin Physiological Phenomena
chemical_list: D001896:Boron Compounds; D054815:Cyclic Nucleotide-Gated Cation Channels; C109986:2-aminoethoxydiphenyl borate; D004110:Diltiazem; D006152:Cyclic GMP