ABSTRACT
The pharmacological actions of parasympathomimetic amines may therefore, in general, be predicted from the knowledge of the body's responses to parasympathetic nerve stimulation. In these instances the tissues may produce responses–muscarinic responses. The role of the parasympathetic vigil innervation in the control of gastrointestinal motility has been described under the enteric nervous system. Parasympathetic nerve stimulation and exogenously added Ach increase peristaltic activity, raise the tone and amplitude of contractions, and enhance the secretory activity of the gastrointestinal tract. Ach increases the secretory activity of the exocrine glands of the gastrointestinal tract. Vagal parasympathetic nerve stimulation to the stomach causes an increase in both the acid and pepsin output from the stomach. These responses are blocked by atropine and are therefore mediated via muscarinic receptors, which are of the M3 subtype. The parasympathetic nerves also supply the submucosal glands where Ach released M3 receptors promotes an increased volume of mucus secretion but not of its composition.
