Gastrointestinal alterations produced by hipothalamic lesions

Abstract

A study is made of the morphological changes which appear in the gastrointestinal tract during lesions made by electrocoagulation in various hypothalamic nuclei. Localisation of these nuclei has been realized according to a cartesian stereotaxic prodecure, with a modified Horsley- Clark apparatus and a cerebral atlas of the guinea pig made by the author. Checking of the localisation of the hypothalamic lesions was done by histological study of the hypothalamus of operated animals. The morphological gastroduodenal lesions were also studied histologically: fixation in Bouin liquid, paraffin inclusion, azan staining, hematoxylineosin, etc.

The total number of animals operated was 30. In 10 of these animals the paraventricular nucleus and its immediate vicinity was coagulated, a good localisation being obtained in 9 of them ; in another 10 the ventromedial hypothalamic nucleus was coagulated, precise localisation being reached in 7 cases; electrocoagulation of the dorsomedial hypothalamic nucleus was practised in another 10 animals, 6 giving a good localisation, and finally in 6 animals the mammillary body and posterior hypothalamic nucleus were electrocoagulated, a good localisation being obtained in three cases.

Results obtained in the cases which presented a good localisation of the lesions were as follows: in the group in which the paraventricular nucleus was coagulated, and also that of the ventromedial nucleus and tuber, gastrointestinal lesions appeared. In the group in which electrocoagulation occurred in the dorsomedial hypothalamic nucleus, gastroduodenal changes appeared only on injection of a lethal dose of diphtheria toxin. Finally in the group in which the mammillary body and posterior hypothalamic nucleus were coagulated no gastrointestinal changes appeared.

These gastrointestinal changes were localised predominantly in the pyloric region, in the lesser curvature of the stomach and in the first portion of the duodenum.

The structural changes present were: first, capillary vasodilation, oedema, and in more localised zones hemorrhages; these changes fundamentally affected the submucous and to a lesser degree the mucous. membrane. In the guinea-pigs in which the lesions had been produced a considerable time before their death (the survival time given was 7-10 days) these presented zones of necrosed tissue, loss of substance being seen at some points.

The mechanism which explains these gastroduodenal changes is believed by the author to be the following: As the hypothalamic nuclei which appear most closely related to the gastroduodenal changes, as shown in this work, are those of the anterior portion of the hypothalamus — a region admitted by nearly all authors to be of parasympathetic nature— on eliminating these nuclei by electrocoagulation, the facilitating tone of these on the vagal nuclei would be diminished. Thus sympathetic tone would predominate on the stomach. This would lead to a vasoconstriction and thus to faulty nutrition of the tissue, with accumulation of vasodilator metabolites, these in turn giving rise to a secondary vasodilatation with oedema, etc., which would cause a continuation of the State of malnutrition of the tissue in which would be produced infarcts after the hemorrhages due to change in the vessel wall, etc.