title: Characterization of Channelrhodopsin and Archaerhodopsin in Cholinergic Neurons of Cre-Lox Transgenic Mice.
abstract: The study of cholinergic signaling in the mammalian CNS has been greatly facilitated by the advent of mouse lines that permit the expression of reporter proteins, such as opsins, in cholinergic neurons. However, the expression of opsins could potentially perturb the physiology of opsin-expressing cholinergic neurons or mouse behavior. Indeed, the published literature includes examples of cellular and behavioral perturbations in preparations designed to drive expression of opsins in cholinergic neurons. Here we investigate expression of opsins, cellular physiology of cholinergic neurons and behavior in two mouse lines, in which channelrhodopsin-2 (ChR2) and archaerhodopsin (Arch) are expressed in cholinergic neurons using the Cre-lox system. The two mouse lines were generated by crossing ChAT-Cre mice with Cre-dependent reporter lines Ai32(ChR2-YFP) and Ai35(Arch-GFP). In most mice from these crosses, we observed expression of ChR2 and Arch in only cholinergic neurons in the basal forebrain and in other putative cholinergic neurons in the forebrain. In small numbers of mice, off-target expression occurred, in which fluorescence did not appear limited to cholinergic neurons. Whole-cell recordings from fluorescently-labeled basal forebrain neurons revealed that both proteins were functional, driving depolarization (ChR2) or hyperpolarization (Arch) upon illumination, with little effect on passive membrane properties, spiking pattern or spike waveform. Finally, performance on a behavioral discrimination task was comparable to that of wild-type mice. Our results indicate that ChAT-Cre x reporter line crosses provide a simple, effective resource for driving indicator and opsin expression in cholinergic neurons with few adverse consequences and are therefore an valuable resource for studying the cholinergic system.
authors.affiliation: Northwestern University, 303 E Chicago Ave, Chicago IL 60611, United States of America.
authors.forename: Tristan
authors.initials: T
authors.lastname: Hedrick
authors.affiliation: Allen Institute for Brain Science, 551 N 34th St, Seattle WA 98103, United States of America.
authors.forename: Bethanny
authors.initials: B
authors.lastname: Danskin
authors.affiliation: Allen Institute for Brain Science, 551 N 34th St, Seattle WA 98103, United States of America.
authors.forename: Rylan S
authors.initials: RS
authors.lastname: Larsen
authors.affiliation: Allen Institute for Brain Science, 551 N 34th St, Seattle WA 98103, United States of America.
authors.forename: Doug
authors.initials: D
authors.lastname: Ollerenshaw
authors.affiliation: Allen Institute for Brain Science, 551 N 34th St, Seattle WA 98103, United States of America.
authors.forename: Peter
authors.initials: P
authors.lastname: Groblewski
authors.affiliation: Allen Institute for Brain Science, 551 N 34th St, Seattle WA 98103, United States of America.
authors.forename: Matthew
authors.initials: M
authors.lastname: Valley
authors.affiliation: Allen Institute for Brain Science, 551 N 34th St, Seattle WA 98103, United States of America.
authors.forename: Shawn
authors.initials: S
authors.lastname: Olsen
authors.affiliation: Allen Institute for Brain Science, 551 N 34th St, Seattle WA 98103, United States of America.
authors.forename: Jack
authors.initials: J
authors.lastname: Waters
mesh_terms: D000200:Action Potentials / Q000502:physiology*; D000818:Animals; D066187:Basal Forebrain / Q000378:metabolism*; D000075402:Channelrhodopsins; D059329:Cholinergic Neurons / Q000378:metabolism*; D005260:Female; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D055355:Opsins / Q000378:metabolism; D015398:Signal Transduction
chemical_list: D000075402:Channelrhodopsins; D055355:Opsins