Vagus

Choline was isolated from ox bile in 1849 by Strecker. During 1900 to 1920, observations led to interest in the vasodepressor properties of the esters of choline, and in the 1920s it was shown that acetylcholine was presumably the "vagus-substance." The nutritional importance of choline was recognized in the 1930s, when it was found that choline would prevent fatty infiltration of the Hver in rats. Subsequent observations showed that choline deficiency could produce cirrhosis (1) or hemorrhagic kidneys (2) in experimental animals under various conditions. 

Vagusstoff, m. vagus substance, acetylcholine or (2.Vaguasto F) thiamine. 

In the gastrointestinal tract, drugs or toxins, as well as mechanical stimulation, induce emesis by activation of sensory receptors on afferent neurons in the vagus and sympathetic nerves. Information is relayed to the vomiting centre via the nucleus tractus solitarius... 

The most widely used emetic is syrup of ipecac, containing the alkaloids, emetine and cq haeline. Emetine induces vomiting by activation of sensory neurons in the vagus and sympathetic nerves to the stomach and centrally in the medulla, possibly at the CTZ. The release of serotonin and SP may be involved as 5-HT3 and NKi receptor antagonists prevent emesis induced... 

The histamine H2-receptor (359 amino acids) is best known for its effect on gastric acid secretion. Histamine H2-receptor activation, in conjunction with gastrin and acetylcholine from the vagus, potently stimulate acid secretion from parietal cells. High concentrations of histamine are also present in cardiac tissues and can stimulate positive chronotropic and inotropic effects via H2-receptor stimulation and activation of adenylyl... 

Substance P is a member of a group of polypeptides known as neurokinins or tachykinins. It is thought to be the primary neurotransmitter for the transfer of sensory information from the periphery to the spinal cord and brain. Substance P as well as neurokinin NKX receptors has been detected in vagal afferent neurons in the area postrema, nucleus tractus solitarius and dorsal motor nucleus of the vagus. Substance P has been shown to increase the firing rate of neurons in the area postrema and nucleus tractus solitarius and to produce retching when applied directly to these areas in animal studies. 

Vagus nerve stimulation (VNS) may be used for adult patients with treatment-resistant depression. A pulse generator is surgically implanted under the skin of the left chest, and an electrical lead connects the generator to the left vagus nerve. Stimulation of this nerve sends signals to the brain. This therapy is intended to be used along with traditional therapies, such as pharmacotherapy and ECT.20... 

Parasympathetic stimulation decreases heart rate. Acetylcholine, the neurotransmitter released from the vagus nerve (the parasympathetic nerve to the heart), binds to muscarinic receptors and causes the following effects ... 

The effects of the autonomic nervous system on MAP are summarized in Figure 15.4. The parasympathetic system innervates the SA node and the AV node of the heart. The major cardiovascular effect of parasympathetic stimulation, by way of the vagus nerves, is to decrease HR, which decreases CO and MAP. 

Pulmonary stretch receptors are responsible for initiating the Hering-Breuer reflex. These stretch receptors are located within the smooth muscle of large and small airways. They are stimulated when the tidal volume exceeds 1 1. Nerve impulses are transmitted by the vagus nerve to the medullary respiratory center and inhibit the inspiratory neurons. The primary function of these receptors and the Hering-Breuer reflex is to prevent overinflation of the lungs. 

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