Abstract
The objective of this study was to investigate the effects of 2% L-glutamine supplementation on myenteric innervation in the ileum of diabetic rats, grouped as follows: normoglycemic (N); normoglycemic supplemented with L-glutamine (NG); diabetic (D); and diabetic supplemented with L-glutamine (DG). The ileums were subjected to immunohistochemical techniques to localize neurons immunoreactive to HuC/D protein (HuC/D-IR) and neuronal nitric oxide synthase enzyme (nNOS-IR) and to analyze varicosities immunoreactive to vasoactive intestinal polypeptide (VIP-IR) and calcitonin gene-related peptide (CGRP-IR). L-Glutamine in the DG group (i) prevented the increase in the cell body area of nNOS-IR neurons, (ii) prevented the increase in the area of VIP-IR varicosities, (iii) did not prevent the loss of HuC/D-IR and nNOS-IR neurons per ganglion, and (iv) reduced the size of CGRP-IR varicosities. L-Glutamine in the NG group reduced (i) the number of HuC/D-IR and nNOS-IR neurons per ganglion, (ii) the cell body area of nNOS-IR neurons, and (iii) the size of VIP-IR and CGRP-IR varicosities. 2% L-glutamine supplementation exerted differential neuroprotective effects in experimental diabetes neuropathy that depended on the type of neurotransmitter analyzed. However, the effects of this dose of L-glutamine on normoglycemic animals suggests there are additional actions of this beyond its antioxidant capacity.
Highlights
The myenteric and submucous plexus, the main components of the enteric nervous system (ENS), contain sensory neurons, interneurons, and motor neurons
The present study investigated the effects of 2% L-glutamine supplementation on diabetesinduced changes in the neurons and varicosities of myenteric fibers in the ileum
The present experimental model of diabetes was confirmed by high levels of glycated hemoglobin and the establishment of diabetic autonomic neuropathy, reflected by a reduction of the total population of myenteric neurons in the ileum
Summary
The myenteric and submucous plexus, the main components of the enteric nervous system (ENS), contain sensory neurons, interneurons, and motor neurons. Myenteric neurons are predominantly involved in the control of muscle contractions, and neurons from the submucous plexus mainly regulate mucosal secretomotor and vasomotor activities (Costa et al 1996, Furness 2006). Extensive experimentation allows corre lation between the expression of identifiable neurochemicals and the function of the enteric neurons, a phenomenon known as the chemical code (Hansen 2003). The chemical code is plastic and changes can occur in response to pathophysiological conditions (Furness 2006, Hansen 2003, Olsson and Holmgren 2010).
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