title: Cholinergic neurons in the mouse rostral ventrolateral medulla target sensory afferent areas.
abstract: The rostral ventrolateral medulla (RVLM) primarily regulates respiration and the autonomic nervous system. Its medial portion (mRVLM) contains many choline acetyltransferase (ChAT)-immunoreactive (ir) neurons of unknown function. We sought to clarify the role of these cholinergic cells by tracing their axonal projections. We first established that these neurons are neither parasympathetic preganglionic neurons nor motor neurons because they did not accumulate intraperitoneally administered Fluorogold. We traced their axonal projections by injecting a Cre-dependent vector (floxed-AAV2) expressing either GFP or mCherrry into the mRVLM of ChAT-Cre mice. Transduced neurons expressing GFP or mCherry were confined to the injection site and were exclusively ChAT-ir. Their axonal projections included the dorsal column nuclei, medullary trigeminal complex, cochlear nuclei, superior olivary complex and spinal cord lamina III. For control experiments, the floxed-AAV2 (mCherry) was injected into the RVLM of dopamine beta-hydroxylase-Cre mice. In these mice, mCherry was exclusively expressed by RVLM catecholaminergic neurons. Consistent with data from rats, these catecholaminergic neurons targeted brain regions involved in autonomic and endocrine regulation. These regions were almost totally different from those innervated by the intermingled mRVLM-ChAT neurons. This study emphasizes the advantages of using Cre-driver mouse strains in combination with floxed-AAV2 to trace the axonal projections of chemically defined neuronal groups. Using this technique, we revealed previously unknown projections of mRVLM-ChAT neurons and showed that despite their close proximity to the cardiorespiratory region of the RVLM, these cholinergic neurons regulate sensory afferent information selectively and presumably have little to do with respiration or circulatory control.
authors.affiliation: Department of Pharmacology, University of Virginia Health System, P.O. Box 800735, 1300 Jefferson Park Avenue, Charlottesville, VA 22908-0735, USA. rs3j@virginia.edu
authors.forename: Ruth L
authors.initials: RL
authors.lastname: Stornetta
authors.forename: Conrad J
authors.initials: CJ
authors.lastname: Macon
authors.forename: Thanh M
authors.initials: TM
authors.lastname: Nguyen
authors.forename: Melissa B
authors.initials: MB
authors.lastname: Coates
authors.forename: Patrice G
authors.initials: PG
authors.lastname: Guyenet
mesh_terms: D059331:Adrenergic Neurons / Q000378:metabolism / Q000502:physiology; D000344:Afferent Pathways / Q000502:physiology; D000818:Animals; D015415:Biomarkers / Q000378:metabolism; D002395:Catecholamines / Q000378:metabolism; D002795:Choline O-Acetyltransferase / Q000235:genetics / Q000378:metabolism; D002799:Cholinergic Fibers / Q000378:metabolism / Q000502:physiology*; D000229:Dependovirus / Q000235:genetics; D004299:Dopamine beta-Hydroxylase / Q000235:genetics; D005260:Female; D005456:Fluorescent Dyes / Q000008:administration & dosage; D005822:Genetic Vectors; D049452:Green Fluorescent Proteins / Q000096:biosynthesis / Q000235:genetics; D007150:Immunohistochemistry; D007274:Injections, Intraperitoneal; D019426:Integrases / Q000235:genetics; D008164:Luminescent Proteins / Q000096:biosynthesis / Q000235:genetics; D008297:Male; D008526:Medulla Oblongata / Q000166:cytology / Q000378:metabolism / Q000502:physiology*; D051379:Mice; D008822:Mice, Transgenic; D056347:Neuroanatomical Tract-Tracing Techniques; D056325:Neuronal Tract-Tracers / Q000008:administration & dosage; D011401:Promoter Regions, Genetic; D012677:Sensation; D011984:Sensory Receptor Cells / Q000378:metabolism / Q000502:physiology*; D013266:Stilbamidines / Q000008:administration & dosage; D014161:Transduction, Genetic; D014446:Tyrosine 3-Monooxygenase / Q000378:metabolism; D000097573:Red Fluorescent Protein
chemical_list: D015415:Biomarkers; D002395:Catecholamines; D002795:Choline O-Acetyltransferase; D004299:Dopamine beta-Hydroxylase; D005456:Fluorescent Dyes; D049452:Green Fluorescent Proteins; D019426:Integrases; D008164:Luminescent Proteins; D056325:Neuronal Tract-Tracers; D013266:Stilbamidines; D014446:Tyrosine 3-Monooxygenase; D000097573:Red Fluorescent Protein; C049774:2-hydroxy-4,4'-diamidinostilbene, methanesulfonate salt; C045073:Cre recombinase