title: Characterization of myenteric interneurons with somatostatin immunoreactivity in the guinea-pig small intestine.
abstract: The projections, connections, morphology and electrophysiological features of the myenteric interneurons with somatostatin immunoreactivity in the guinea-pig small intestine have been established using retrograde tracing, immunohistochemistry, confocal microscopy and intracellular recording. After application of the fluorescent dye, 1,1'-didodecyl-3,3,3',3'-tetramethyl indocarbocyanine perchlorate (DiI), to the myenteric plexus, up to 900 nerve cell bodies were labelled in each preparation. Somatostatin-immunoreactive neurons accounted for 13% of all retrogradely labelled cells and were located up to 70 mm orally. When DiI was applied to the submucous ganglia, many myenteric neurons were labelled and 8% of all retrogradely labelled cells were somatostatin immunoreactive and were located up to 60 mm oral to the DiI application sites. These neurons had ovoid cell bodies, a single axon, several long filamentous dendrites and received close contacts from 40-200 somatostatin-immunoreactive varicosities. Intracellular recordings revealed that these cells had features of both S (i.e. with Synaptic inputs) and AH (i.e. neurons with After Hyperpolarization) cells, receiving fast excitatory synaptic inputs, having characteristic "sag" in their response to hyperpolarizing current pulses and sometimes a long afterhyperpolarization following soma action potentials. It is concluded that somatostatin-immunoreactive neurons have distinct electrophysiological features and form very long anally directed interneuronal chains that connect with both myenteric and submucous neurons.
authors.affiliation: Department of Human Physiology and Centre for Neuroscience, The Flinders University of South Australia, Adelaide.
authors.forename: Z M
authors.initials: ZM
authors.lastname: Song
authors.forename: S J
authors.initials: SJ
authors.lastname: Brookes
authors.forename: G A
authors.initials: GA
authors.lastname: Ramsay
authors.forename: M
authors.initials: M
authors.lastname: Costa
mesh_terms: D000818:Animals; D001370:Axonal Transport; D001369:Axons / Q000502:physiology / Q000648:ultrastructure; D002232:Carbocyanines; D003712:Dendrites / Q000502:physiology / Q000648:ultrastructure; D005456:Fluorescent Dyes; D005725:Ganglia, Autonomic / Q000166:cytology / Q000502:physiology; D006168:Guinea Pigs; D007150:Immunohistochemistry; D007395:Interneurons / Q000166:cytology* / Q000502:physiology; D007421:Intestine, Small / Q000166:cytology / Q000294:innervation*; D009197:Myenteric Plexus / Q000166:cytology* / Q000502:physiology; D013004:Somatostatin / Q000032:analysis*; D013569:Synapses / Q000502:physiology / Q000648:ultrastructure
chemical_list: D002232:Carbocyanines; D005456:Fluorescent Dyes; D013004:Somatostatin; C072024:carbocyanine dye DiIC12(3)