The Effect Of Hemorrhagic Shock On Jejunal Motility In Rats

ObjectiveHemorrhagic shock (HS) impairs the normal intestinal motility. Bacterial overgrowth secondary to intestinal motility disorder plays an important role in bacterial translocation, which is known as an predisposing factor to the multiple organ failure (MOF). In addition, the disturbed intestinal motility may necessitate parenteral nutrition and prolong hospitalization. In the enteric nervous system (ENS), acetylcholine (ACh) is one of major excitatory transmitter, released from cholinergic neurons. Activation of cholinergic neurons can elicit a depolarization and contraction of smooth muscle, mediated by ACh. Nitric oxide (NO), released from neuronal nitric oxide synthase (nNOS) expressing neurons is a principal non-adrenergic non-cholinergic (NANC) neurotransmitter in the ENS. Our aim was to investigate the effect of HS on the enteric motor function and the alteration of myenteric neurons in a rat model.Materials and MethodsSprague-Dawley rats were randomly divided into control group and HS group. HS group rats were subjected to severe hemorrhagic shock (mean arterial pressure 40 mm Hg for 90 min) followed by resuscitation. Control group rats underwent cannulation and anesthesia for an identical period of time as shock animals but were not bled. Both HS group and control group were killed at 6 h after resuscitation. Rats in each group were gavaged with Evans blue, and then the transmission of Evans blue in small intestine was determined. Jejunum segments were used for vitro contractility studies. The spontaneous mechanical contractions and contractile response to acetylcholine (ACh), KCl, TTX, the nitric oxide synthase (NOS) inhibitor Nω-Nitro-L-arginine (L-NNA) as well as inducible nitric oxide synthase inhibitor Aminoguanidine (AG) were evaluated by organ bath technique. The amplitude, frequency and area under curve (AUC) of jejunum contractions were recorded for analysis. The expressions of PGP9.5, choline acetyltransferase (ChaT) and nNOS and in the myenteric plexus (MP) were evaluated by immunofluorescence staining and Western-blot.Results The propellant velocity of Evans blue was slower in HS group than the control group (P<0.05). The amplitude of spontaneous contractions of jejunum smooth muscular significantly decreased (p< 0.05) in HS group compared with control group. However, the frequency of spontaneous contractions of jejunum smooth muscular was not significant difference (p> 0.05) between two groups. The contractile response to ACh, KCl, TTX, and L-NNA declined significantly (p< 0.05) in HS group. However, the amplitude of spontaneous contractions after AG treatment didn't increase significantly in both groups (p > 0.05). The immunopositivity area and the integrated optical density (IOD) of PGP9.5 in MP were significantly decreased (p< 0.05) in HS group. The ChaT immunopositivity area, IOD, the number of ChaT immunoreactive neurons/ganglion and the ChaT protein expression in the MP of HS rats were significantly reduced (p< 0.05) in HS group. The nNOS immunopositivity area, IOD, the number of nNOS immunoreactive neurons/ganglion and the nNOS protein expression in the MP of HS rats were also significantly reduced (p< 0.05) in HS group.ConclusionOur result suggested that intestinal motility was impaired in a rat model of HS and the damage of cholinergic neurons and nitregic neurons in myenteric nerves might be a underlying mechanism of the intestinal motor dysfunction.