title: Identification of optogenetically activated striatal medium spiny neurons by Npas4 expression.
abstract: Optogenetics is a powerful neuromodulatory tool with many unique advantages to explore functions of neuronal circuits in physiology and diseases. Yet, interpretation of cellular and behavioral responses following in vivo optogenetic manipulation of brain activities in experimental animals often necessitates identification of photoactivated neurons with high spatial resolution. Although tracing expression of immediate early genes (IEGs) provides a convenient approach, neuronal activation is not always followed by specific induction of widely used neuronal activity markers like c-fos, Egr1 and Arc. In this study we performed unilateral optogenetic stimulation of the striatum in freely moving transgenic mice that expressed a channelrhodopsin-2 (ChR2) variant ChR2(C128S) in striatal medium spiny neurons (MSNs). We found that in vivo blue light stimulation significantly altered electrophysiological activity of striatal neurons and animal behaviors. To identify photoactivated neurons we then analyzed IEG expression patterns using in situ hybridization. Upon light illumination an induction of c-fos was not apparent whereas another neuronal IEG Npas4 was robustly induced in MSNs ipsilaterally. Our results demonstrate that tracing Npas4 mRNA expression following in vivo optogenetic modulation can be an effective tool for reliable and sensitive identification of activated MSNs in the mouse striatum.
authors.affiliation: Department of Morphological Neural Science, Graduate School of Medical Sciences, Kumamoto University, Kumamoto, Japan.
authors.forename: Asim K
authors.initials: AK
authors.lastname: Bepari
authors.forename: Hiromi
authors.initials: H
authors.lastname: Sano
authors.forename: Nobuaki
authors.initials: N
authors.lastname: Tamamaki
authors.forename: Atsushi
authors.initials: A
authors.lastname: Nambu
authors.forename: Kenji F
authors.initials: KF
authors.lastname: Tanaka
authors.forename: Hirohide
authors.initials: H
authors.lastname: Takebayashi
mesh_terms: D019943:Amino Acid Substitution; D000818:Animals; D051792:Basic Helix-Loop-Helix Proteins / Q000235:genetics* / Q000378:metabolism; D000075402:Channelrhodopsins; D015870:Gene Expression; D017781:Genes, Immediate-Early; D008027:Light; D008564:Membrane Potentials; D051379:Mice; D008822:Mice, Transgenic; D009068:Movement; D017072:Neostriatum / Q000166:cytology* / Q000502:physiology / Q000528:radiation effects; D009474:Neurons / Q000378:metabolism* / Q000502:physiology / Q000528:radiation effects; D062308:Optogenetics
chemical_list: D051792:Basic Helix-Loop-Helix Proteins; D000075402:Channelrhodopsins; C533005:Npas4 protein, mouse