title: Co-localization of Gamma-Aminobutyric Acid and Glutamate in Neurons of the Spider Central Nervous System.
abstract: Spider sensory neurons with cell bodies close to various sensory organs are innervated by putative efferent axons from the central nervous system (CNS). Light and electronmicroscopic imaging of immunolabeled neurons has demonstrated that neurotransmitters present at peripheral synapses include γ-aminobutyric acid (GABA), glutamate and octopamine. Moreover, electrophysiological studies show that these neurotransmitters modulate the sensitivity of peripheral sensory neurons. Here, we undertook immunocytochemical investigations to characterize GABA and glutamate-immunoreactive neurons in three-dimensional reconstructions of the spider CNS. We document that both neurotransmitters are abundant in morphologically distinct neurons throughout the CNS. Labeling for the vesicular transporters, VGAT for GABA and VGLUT for glutamate, showed corresponding patterns, supporting the specificity of antibody binding. Whereas some neurons displayed strong immunolabeling, others were only weakly labeled. Double labeling showed that a subpopulation of weakly labeled neurons present in all ganglia expresses both GABA and glutamate. Double labeled, strongly and weakly labeled GABA and glutamate immunoreactive axons were also observed in the periphery along muscle fibers and peripheral sensory neurons. Electron microscopic investigations showed presynaptic profiles of various diameters with mixed vesicle populations innervating muscle tissue as well as sensory neurons. Our findings provide evidence that: (1) sensory neurons and muscle fibers are innervated by morphologically distinct, centrally located GABA- and glutamate immunoreactive neurons; (2) a subpopulation of these neurons may co-release both neurotransmitters; and (3) sensory neurons and muscles are innervated by all of these neurochemically and morphologically distinct types of neurons. The biochemical diversity of presynaptic innervation may contribute to how spiders filter natural stimuli and coordinate appropriate response patterns.
authors.affiliation: Department of Psychology and Neuroscience, Life Sciences Centre, Dalhousie University, 1355 Oxford Street, P.O. Box 15000, Halifax, Nova Scotia, Canada, B3H 4R2. rfabianf@dal.ca.|Department of Biology, Saint Michael's College, One Winooski Park, Colchester, VT, 05439, USA. rfabianf@dal.ca.
authors.forename: Ruth
authors.initials: R
authors.lastname: Fabian-Fine
authors.affiliation: Department of Physiology and Biophysics, Dalhousie University, PO Box 15000, Halifax, Nova Scotia, Canada, B3H 4R2.
authors.forename: Shannon
authors.initials: S
authors.lastname: Meisner
authors.affiliation: Department of Physiology and Biophysics, Dalhousie University, PO Box 15000, Halifax, Nova Scotia, Canada, B3H 4R2.
authors.forename: Päivi H
authors.initials: PH
authors.lastname: Torkkeli
authors.affiliation: Department of Psychology and Neuroscience, Life Sciences Centre, Dalhousie University, 1355 Oxford Street, P.O. Box 15000, Halifax, Nova Scotia, Canada, B3H 4R2.
authors.forename: Ian A
authors.initials: IA
authors.lastname: Meinertzhagen
mesh_terms: D000818:Animals; D002490:Central Nervous System / Q000378:metabolism*; D004947:Esophagus / Q000378:metabolism; D005260:Female; D005455:Fluorescent Antibody Technique; D050485:GABA Plasma Membrane Transport Proteins / Q000378:metabolism; D017952:Ganglia, Invertebrate / Q000378:metabolism; D018698:Glutamic Acid / Q000378:metabolism*; D021621:Imaging, Three-Dimensional; D009132:Muscles / Q000378:metabolism / Q000648:ultrastructure; D009474:Neurons / Q000378:metabolism*; D013112:Spiders / Q000378:metabolism* / Q000648:ultrastructure; D013569:Synapses / Q000378:metabolism / Q000648:ultrastructure; D005680:gamma-Aminobutyric Acid / Q000378:metabolism*
chemical_list: D050485:GABA Plasma Membrane Transport Proteins; D018698:Glutamic Acid; D005680:gamma-Aminobutyric Acid
keywords: Cupiennius salei; GABA/Glutamate co-transmission; Spider muscle; Vesicular GABA transporter; Vesicular glutamate transporter