title: Unraveling the architecture of the dorsal raphe synaptic neuropil using high-resolution neuroanatomy.
abstract: The dorsal raphe nucleus (DRN), representing the main source of brain's serotonin, is implicated in the pathophysiology and therapeutics of several mental disorders that can be debilitating and life-long including depression, anxiety and autism. The activity of DRN neurons is precisely regulated, both phasically and tonically, by excitatory glutamate and inhibitory GABAergic axons arising from extra-raphe areas as well as from local sources within the nucleus. Changes in serotonin neurotransmission associated with pathophysiology may be encoded by alterations within this network of regulatory afferents. However, the complex organization of the DRN circuitry remains still poorly understood. Using a recently developed high-resolution immunofluorescence technique called array tomography (AT) we quantitatively analyzed the relative contribution of different populations of glutamate axons originating from different brain regions to the excitatory drive of the DRN. Additionally, we examined the presence of GABA axons within the DRN and their possible association with glutamate axons. In this review, we summarize our findings on the architecture of the rodent DRN synaptic neuropil using high-resolution neuroanatomy, and discuss possible functional implications for the nucleus. Understanding of the synaptic architecture of neural circuits at high resolution will pave the way to understand how neural structure and function may be perturbed in pathological states.
authors.affiliation: Institut du Fer à Moulin, INSERM, UMR-S 839 Paris, France ; Université Pierre et Marie Curie Paris, France.
authors.forename: Mariano
authors.initials: M
authors.lastname: Soiza-Reilly
authors.affiliation: Department of Anesthesiology, Perioperative, and Pain Medicine, Boston Children's Hospital Boston, MA, USA ; Department of Anaesthesia, Harvard Medical School Boston, MA, USA.
authors.forename: Kathryn G
authors.initials: KG
authors.lastname: Commons
mesh_terms: D000818:Animals; D065847:Dorsal Raphe Nucleus / Q000033:anatomy & histology*; D005455:Fluorescent Antibody Technique; D018698:Glutamic Acid / Q000378:metabolism; D019581:Neuropil / Q000166:cytology* / Q000502:physiology*; D013569:Synapses / Q000378:metabolism / Q000648:ultrastructure*; D014365:Tryptophan Hydroxylase / Q000378:metabolism; D005680:gamma-Aminobutyric Acid / Q000378:metabolism
chemical_list: D018698:Glutamic Acid; D005680:gamma-Aminobutyric Acid; D014365:Tryptophan Hydroxylase
keywords: axo-axonic; glutamate decarboxylase 65; synapses; ultrathin serial-sections; vesicular glutamate transporter