Assessment of NADPH-diaphorase stained myenteric neurons of the jejunum of diabetic rats supplemented with ascorbic acid

Abstract

The relation between hyperglycemia and diabetic neuropathy has already been demonstrated in some studies. Among the theories proposed for its etiology the oxidative stress stands out. The performance of nitric oxide as a link between the metabolic and vascular neuropathogenic factors that triggers the diabetic neuropathy has already been put forward. This study aimed to assess the quantification and measurements of the cell body profile area (CBPA) of NADPH-diaphorase reactive (NADPH-dp) myenteric neurons of the jejunum of diabetic rats (induced by streptozotocin) supplemented with Ascorbic Acid (AA). These changes in the myenteric neurons seem to be related to the gastrointestinal disturbances observed in diabetes mellitus (DM). Twenty male Wistar rats (Rattus norvegicus) were distributed in 4 groups (n=5): controls (C), control supplemented (CS), diabetic (D), and diabetic suplemented (DS). DM was induced by estreptozotocin (50mg/kg body wt). One week after the induction and confirmation of the DM (glycemia exam), animals of the groups CS and DS received 50mg of AA three times a week by gavage. After 90 days of experiment, the animals were anesthetized with lethal thiopental dose (40mg/kg) and the collected jejunum processed for the histochemistry NADPH-diaphorase technique. Whole-mount preparations were obtained for quantitative and morphometric analysis of the myenteric neurons. A quantity of jejunum neurons in the Group D (96±7.5) was not different (P>0.05) from Group DS (116±8.08), C (92±9.7), and CS (81±5.4), but in Group DS the quantity was higher (P<0.05) than in Group C and CS. The CBPA of neurons from Group D (189.50±2.68µm²) and DS (195.92±3.75µm²) were lower (P<0.05) than from Group C (225.13±4.37µm²) and CS (210.23±3.15µm²). The streptozotocin-induced DM did not change the jejunum-ileum area, the jejunum myenteric plexus space organization and the density of NADPH-dp neurons. The 50g AA-supplementation, three times a week, during 90 days, did not decrease hyperglycemia; however, it had a neuroprotective effect on the myenteric neurons, minimizing the increase on the CBPA of NADPH-dp neurons and increasing the amount of NADPD-dp neurons.

Effects of ascorbic acid supplementation in ileum myenteric neurons of streptozotocin-induced diabetic rats

“…The PC areas in Group DS and CS were 12.7% and 27.5% lower when compared to Group D and C, respectively (Table 2). A similar effect of the AA treatment on the PC area of diabetic animals is reported in the jejunum (Silverio et al 2008) and in the ileum of rats that remained diabetic for 120 days (Zanoni et al 2003).…”

“…Zanoni et al (2003) and Silverio et al (2008) have also found a decreased frequency of neurons in the PC area exceeding 200ìm 2 and an increased incidence of neurons with a PC area lower less than to 200ìm 2 in the ileum and jejunum of myenteric plexus of STZ-induced diabetic rats AA-treated, although with not with the same percentage.…”

“…In higher vertebrates, the neuron organization in the myenteric plexus forming ganglia interconnected by nerve fibers between the muscle layer strata of the gastro-intestinal segments is well described in the literature (Gabella 1979, 1990, Molinari et al 1994, Sant'Ana et al 1997, Furness 2000, Mari et al 2007, Silva et al 2008) and is not modified by diabetes (Zanoni et al 1997, 2003, Silverio et al 2008. Similarly, the plexus organization remained unchanged among the groups studied (C, CS, DS, and D), not changing either with the diabetes onset and or by the AA-supplementation.…”

“…Experimental period longer than 90 days cause less weight gain for diabetic animals (Zanoni et al 2003, Clebis et al 2004, Fregonesi et al 2005, Silverio et al 2008.…”

“…Changes in neurons of the myenteric plexus have been described in different conditions and experimental models which have tried to elucidate the mechanisms that lead to functional impairment of the digestive tube (Fregonesi et al 2001, Furlan et al 2002, Zanoni et al 2003, Fontes et al 2004, Alves et al 2006, Araújo et al 2006, Silverio et al 2008, Silva et al 2008.…”