Quantitative analysis of inputs to somatostatin-immunoreactive descending interneurons in the myenteric plexus of the guinea-pig small intestine.
Somatostatin immunoreactivity occurs in a specific subgroup of cholinergic descending interneurons in the myenteric plexus of the guinea-pig small intestine. In the present work, we made light- and electron-microscopic investigations of chemically defined inputs to these neurons, in order that the origins of the connections of other neurons with them could be deduced. Somatostatin-immunoreactive synapses and close contacts were found on the cell bodies and filamentous processes of somatostatin neurons; these were 84% of all inputs. It is thus confirmed that this class of interneuron forms chains that project anally. Descending interneurons with immunoreactivity for nitric oxide synthase provided 14% of inputs to somatostatin-immunoreactive descending interneurons. An antiserum against a calcium-binding protein, calbindin, was used as marker for the majority of intrinsic primary afferent neurons, AH/Dogiel type II neurons; this class of neurons provided only 2.5% of the inputs to somatostatin-immunoreactive descending interneurons. We conclude that somatostatin-immunoreactive descending interneurons are involved in the conduction of impulses distally along the full length of the small intestine, but receive only a minor input from calbindin-immunoreactive primary afferent neurons.
Pompolo
S
S
Department of Anatomy and Cell Biology, University of Melbourne, Parkville 3052, Victoria, Australia.
Furness
J B
JB
D000818:Animals; D064026:Calbindins; D005260:Female; D005769:Gastrointestinal Motility / Q000502:physiology; D006168:Guinea Pigs; D007395:Interneurons / Q000737:chemistry* / Q000648:ultrastructure; D007421:Intestine, Small / Q000294:innervation*; D008297:Male; D008854:Microscopy, Electron; D009197:Myenteric Plexus / Q000737:chemistry* / Q000166:cytology*; D009419:Nerve Tissue Proteins / Q000032:analysis; D064030:S100 Calcium Binding Protein G / Q000032:analysis; D013004:Somatostatin / Q000032:analysis* / Q000276:immunology; D013569:Synapses / Q000737:chemistry / Q000502:physiology
D064026:Calbindins; D009419:Nerve Tissue Proteins; D064030:S100 Calcium Binding Protein G; D013004:Somatostatin