Auerbach’s plexus

Enteric nerves control intestinal smooth muscle action and are connected to the brain by the autonomic nervous system. IBS is thought to result from dysregulation of this brain-gut axis. The enteric nervous system is composed of two gan-glionated plexuses that control gut innervation the submucous plexus (Meissner s plexus) and the myenteric plexus (Auerbach s plexus). The enteric nervous system and the central nervous system (CNS) are interconnected and interdependent. A number of neurochemicals mediate their function, including serotonin (5-hydroxytryptamine or 5-HT), acetylcholine, substance P, and nitric oxide, among others. 

Both the parasympathetic and sympathetic nervous systems provide extrinsic gastrointestinal innervation. Parasympathetic stimulation increases muscle contraction of the gut, while sympathetic stimulation inhibits contractions. Stimulation of either a- or 13-adrenoceptors will result in inhibition of contractions. The intramural nervous system consists of a myenteric (Auerbach s) plexus between the circular and longitudinal muscle areas and a submucosal (Meissner s) plexus between the muscularis mucosa and the circular muscle layers. These two plexuses contain stimulatory cholinergic neurons. 

It has been proposed that adrenergic fibers terminate at inhibitory B receptors on smooth muscle fibers, and at inhibitory a receptors on parasympathetic cholinergic (excitatory) ganglion cells of Auerbach s plexus. 

Anthraquinone derivatives include cascara sagrada, sennosides, and casanthrol. Gut bacteria metabolizes these agents to their active compounds, but the exact mechanisms of action are not understood. Effects are limited to the colon, and stimulation of Auerbach s plexus may be involved. Recommendations for the use of these agents are similar to those for the diphenyhnethane derivatives. In most cases, intermittent use is acceptable daily use should be strongly discouraged. 

The activities of the GI tract are controlled locally through a restricted part of the peripheral nervous system called the enteric nervous system (ENS). The ENS is involved in sensorimotor control and consists of both afferent sensory neurons and a number of motor nerves and intemeurons that are organized principally into two nerve plexuses the myenteric (Auerbach s) plexus and the submucosal (Meissner s) plexus. The myenteric plexus, located between the longitudinal and circular muscle layers, plays an important role in the contraction and relaxation of GI smooth muscle. The submucosal plexus is involved with secretory and absorptive functions of the GI epithelium, local blood flow, and neuroimmune activities. The ENS consists of components of the sympathetic and parasympathetic branches of the ANS and has sensory nerve connections through the spinal and nodose ganglia ("see Chapter 37). 

Neostigmine augments GI motor activity the colon is particularly stimulated. Propulsive waves are increased in amplitude and frequency, and movement of intestinal contents is thus promoted. The effect of anti-ChE agents on intestinal motility probably represents a combination of actions at the ganghon cells of Auerbach s plexus and at the smooth muscle fibers (see Chapter 37). 

The gastrointestinal (GI) tract is in a continuous contractile, absorptive, and secretory state. The control of this state is complex, with contributions by the muscle itself, local nerves (i.e., the enteric nervous system, ENS), the central nervous system (CNS), and humoral pathways. Of these, perhaps the most important regulator of physiological gut function is the ENS (Figure 37-1), which is an autonomous collection of nerves within the wall of the Gl tract, organized into two connected networks of neurons the myenteric (Auerbach s) plexus, found between the circular and longitudinal muscle layers, and the submucosal (Meissner s) plexus, found below the epithehum. The former is responsible for motor control, while the latter regulates secretion, fluid transport, and vascular flow. 

The intrinsic innervation of the GIT is considered as a separate autonomic division, called the enteric nervous system (ENS) (Schemann and Neunlist 2004). Neurons and enteric glia of the ENS are embedded within the gut wall and arranged in three plexuses (Hall 2011). The myenteric (Auerbach s) plexus is located between the inner and outer circular muscle layers and the submucosal (Meissner s) plexus between the circular muscle and muscularis mucosa. The deep muscle plexus separates inner and outer circular muscle layers in the small intestine. In the large intestine, it is located at the inner border of circular muscle and is called submucosal plexus. 

The majority of the cell bodies of enteric neurons are found in the two plexuses, the myenteric (Auerbach s plexus) and the submucosal (Meissner s plexus). Because the enteric plexuses of the stomach have not been studied in as much detail as those of the small and large intestines, a description of the organization and function of the gastric enteric neurons relies often on information gleaned from other... 

Before the era of synuclein immunocytochemistry, Qualman et al. (1984) observed in a postmortem study LBs in the esophageal Auerbach plexus of two dysphagic PD patients but not in Meissner s plexus. Subsequently, Wakabayashi et al. (1988) reported LBs and LNs in both plexuses of clinically diagnosed PD patients and asymptomatic incidental cases. In the gut, the bulk of the proteins were observed in cellular processes and cell bodies of vasoactive intestinal polypeptide (VIPergic) neurons (Wakabayashi et al., 1988,1993). 

Micro absence of ganglion cells in Auerbach s and Meissner s plexuses... 

Hirschsprung s disease have ETB receptor mutations). The lack of ET-3/ETB receptor results in the absence of parasympathic ganglionic neurons in the myenteric plexus (Auerbach). Mice with an ET-3/ETB receptor disruption die within 2 weeks after birth. In transgenic mice, in which the expression of the ETB receptor is driven by the dopamine (3-hydroxylase promoter, normal myenteric plexus are present and no enteric disorder develops. These mice, however, show a salt-sensitive hypertension, which can be efficiently treated with amiloride, indicating that ETB receptors are involved in the regulation of natriuresis via the amilorid-sensitive sodium channel ENaC. 

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