Myenteric Plexus Ablation Research Articles

Suppression of c-Kit signaling induces adult neurogenesis in the mouse intestine after myenteric plexus ablation with benzalkonium chloride.

Adult neurogenesis rarely occurs in the enteric nervous system (ENS). In this study, we demonstrated that, after intestinal myenteric plexus (MP) ablation with benzalkonium chloride (BAC), adult neurogenesis in the ENS was significantly induced in c-kit loss-of-function mutant mice (W/Wv). Almost all neurons and fibers in the MP disappeared after BAC treatment. However, 1 week after ablation, substantial penetration of nerve fibers from the non-damaged area was observed in the MP, longitudinal muscle and subserosal layers in both wildtype and W/Wv mice. Two weeks after BAC treatment, in addition to the penetrating fibers, a substantial number of ectopic neurons appeared in the subserosal and longitudinal muscle layers of W/Wv mice, whereas only a few ectopic neurons appeared in wildtype mice. Such ectopic neurons expressed either excitatory or inhibitory intrinsic motor neuron markers and formed ganglion-like structures, including glial cells, synaptic vesicles and basal lamina. Furthermore, oral administration of imatinib, an inhibitor of c-Kit and an anticancer agent for gastrointestinal stromal tumors, markedly induced appearance of ectopic neurons after BAC treatment, even in wildtype mice. These results suggest that adult neurogenesis in the ENS is negatively regulated by c-Kit signaling in vivo.

Ketamine and the Myenteric Plexus in Intestinal Ischemia/Reperfusion Injury

Intestinal ischemia/reperfusion (I/R) is a common clinical entity with severe consequences. We studied the effects of ketamine and the participation of the myenteric plexus in I/R injury. Rats were divided into six groups: sham, IR (30 min ischemia/60 min reperfusion), KET+IR (50 mg/kg i.p. ketamine injection before I/R), DEN (myenteric plexus ablated with benzalkonium chloride (BAC) and sham operation performed), DEN+IR (BAC treated and I/R induced), and DEN+KET+IR (BAC treated, ketamine administered, and I/R induced). Serum concentrations of p-selectin, intracellular adhesion molecule-1 (ICAM-1), and antithrombin III (ATIII) were measured, and tissue samples were obtained for histological analysis. IR group had higher intestinal mucosa injury and elevated serum concentrations of ICAM-1 and p-selectin, as well as ATIII depletion, compared with sham group (P < 0.05). In KET+IR group these alterations were significantly reduced (P < 0.05). DEN group showed ICAM-1 elevations when compared with sham group (P < 0.05), and DEN+IR group showed no difference in any parameter compared with IR group. However, ketamine administration in group DEN+KET+IR had no effect on any parameter when compared with DEN+IR group. Ketamine was able to diminish alterations induced by I/R. Myenteric plexus ablation with BAC treatment alone had no effects on intestinal I/R injury. However, this procedure abolished ketamine's protective effects. Ketamine seems to require an intact enteric nervous system to exert its protective action.

Myenteric denervation differentially reduces enteroendocrine serotonin cell population in rats during postnatal development

The enteric nervous and enteroendocrine systems regulate different processes in the small intestine. Ablation of myenteric plexus with benzalkonium chloride (BAC) stimulates epithelial cell proliferation, whereas endocrine serotonin cells may inhibit the process. To evaluate the connection between the systems and the influence of myenteric plexus on serotoninergic cells in rats during postnatal development, the ileal plexus was partially removed with BAC. Rats were treated at 13 or 21 days and sacrificed after 15 days. The cell bodies of myenteric neurons were stained by beta NADH-diaphorase to detect the extension of denervation. The number of enteroendocrine cells in the ileum was estimated in crypts and villi in paraffin sections immunostained for serotonin. The number of neurons was reduced by 27.6 and 45% in rats treated on the 13th and 21st days, respectively. We tried to establish a correlation of denervation and the serotonin population according to the age of treatment. We observed a reduction of immunolabelled cells in the crypts of rats treated at 13 days, whereas this effect was seen in the villi of rats denervated at 21 days. These results suggest that the enteric nervous system might control the enteroendocrine cell population and this complex mechanism could be correlated to changes in cell proliferation.

Multiple mechanisms contribute to myenteric plexus ablation induced by benzalkonium chloride in the guinea-pig ileum.

Ablation of rat myenteric plexus with benzalkonium chloride has provided a model of intestinal aganglionosis, but the degenerative responses are not well understood. We examined the effects of this detergent on neurons and glia, including expression of c-Myc, c-Jun, JunB, and c-Fos, and on immunocytes in the guinea-pig ileum. Benzalkonium chloride (0.1%) or saline was applied to the serosal surface of distal ileum. Tissues were analyzed 2, 3, or 7 days later and compared with cyclosporine-treated and untreated animals. More than 90% of myenteric neurons were destroyed in ileal segments 3-7 days after benzalkonium-chloride treatment. Glia withdrew processes from around neurons after 2 days and were mostly gone after 3 days. Neuronal c-Myc began to disappear while c-Fos, c-Jun, and JunB were evident in some neuronal nuclei after 2 or 3 days. After 3 days, widespread apoptosis was evident in the myenteric plexus. Populations of T cells, B cells, and macrophage-like cells in untreated and saline-treated myenteric plexuses were substantially increased 3 and 7 days after benzalkonium-chloride treatment. Cyclosporine delayed significant neuronal loss. We conclude that a variety of degenerative mechanisms may be active in this model, including an immune response which may actively contribute to tissue destruction.

Altered carbachol-induced contractile responses of rat jejunal smooth muscle following local myenteric plexus ablation

Alterations in smooth muscle responsiveness and neural pathways in adjacent tissue may occur after local myenteric denervation. The in vitro contractile responses of both longitudinal and circular muscle to the mixed muscarinic and nicotinic cholinergic agonist carbachol were determined 15, 30, and 45 days after localized myenteric plexus ablation. Denervated longitudinal muscle exhibited decreased responsiveness to carbachol at all times examined. Denervated circulated muscle was initially supersensitive, but with time became subsensitive. These changes probably reflect the loss of the nicotinic (neuronal) component of the action of carbachol. Muscle orad to the site of denervation appeared subsensitive, while muscle caudad to the lesion was supersensitive (circular) or unaffected (longitudinal). These results suggest that there are changes in ascending and descending neural pathways. Alterations in the cholinergic responsiveness of intestinal smooth muscle, both at and beyond the site of myenteric plexus ablation, may result in altered intestinal motility that could lead to functional obstruction.

Temporal changes in mechanical properties of rat jejunal smooth muscle after myenteric plexus ablation.

We determined length-stress properties and active tension development of rat jejunal longitudinal and circular muscle at various times after myenteric neuron ablation. Myenteric neurons were destroyed by serosal application of benzalkonium chloride. Active tension generation in response to both carbachol and barium was depressed in both muscle layers up to 7 days after treatment, at which times the responses were normal. At 15 days, circular muscle responses were still comparable to control, but longitudinal muscle responses were significantly increased. Length-stress parameters of circular muscle were minimally affected, while those of longitudinal muscle were significantly altered 15 and 30 days after treatment. These alterations include changes in resting stress and increased active stress generation at both times. Our results suggest that 1) normal myenteric innervation is necessary for normal contractile activity in rat jejunal smooth muscle and 2) changes in cellular or tissue morphology or alterations in intracellular calcium homeostasis, as seen in other tissue, may occur after myenteric plexus ablation.

Temporal changes in sensitivity of muscarinic receptors of rat jejunal smooth muscle following myenteric plexus ablation

Temporal changes in sensitivity of muscarinic receptors of rat jejunal smooth muscle following myenteric plexus ablation

Changes in mechanical properties of rat jejunal smooth muscle with time following myenteric plexus ablation

Changes in mechanical properties of rat jejunal smooth muscle with time following myenteric plexus ablation

Temporal changes in sensitivity of muscarinic receptors of rat jejunal smooth muscle following myenteric plexus ablation

Temporal changes in sensitivity of muscarinic receptors of rat jejunal smooth muscle following myenteric plexus ablation