Cytometrical and Pharmacological Studies on the Function of the Myenteric Plexus in Severe Idiopathic Chronic Constipation

Hirofumi Niwamoto, Shuichi Ohashi*, Eizo Okamoto

The First Department of Surgery, Hyogo College of Medicine
*Department of Surgery, Takarazuka Municipal Hospital

To clarify the functional role of the myenteric plexus in the pathogenesis of severe idiopathic constipation, morphologic studies were carried out on resected specimens of 20 patients treated by subtotal colectomy. The number of myenteric nerve cells of the entire circumference of the colon calculated by an image analyzer was 154±32 in the constipated patients, which was significantly lower than the274±67 in the control. Conversely, the size of the nerve cells represented by the nuclear area was 102.8±30.6 µ² in the constipated group, which was significantly higher than the 62.0±19.6 µ² in the control. The amount of muscarinic acetylcholine receptor measured by [³H] quinuclidinyl benzilate binding assay was significantly higher in the constipated groups (477.0±79.6 fmol/mg protein) than in the control (291.6±31.2 fmol/mg protein). Coincidentally, the dose response curve of the fresh muscle strip to oxotremorine, an agonist of acetylcholine, shifted markedly to the left, indicating the existence of denervation supersensitivity of Cannon. This study suggests that a decrease in cholinergic excitatory neurons and a relative increase in inhibitory neurons of the myenteric plexus may play a significant role in the pathophysiology of severe idiopathic constipation.

Key words
severe idiopathic chronic constipation, Auerbach's plexus, number of ganglion cell, nuclear area of ganglion cell, muscarinic acetylcholine receptor

Reprint requests
Hirofumi Niwamoto The First Department of Surgery, Hyogo College of Medicine
1-1 Mukogawa-cho, Nishinomiya, 663 JAPAN

Accepted
October 7, 1992

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