Abstract
The effects of dorsomedial hypothalamic (DMH) nucleus lesion on body weight, plasma glucose levels, and the gastric emptying of a liquid meal were investigated in male Wistar rats (170-250 g). DMH lesions were produced stereotaxically by delivering a 2.0-mA current for 20 s through nichrome electrodes (0.3-mm tip exposure). In a second set of experiments, the DMH and the ventromedial hypothalamic (VMH) nucleus were lesioned with a 1.0-mA current for 10 s (0.1-mm tip exposure). The medial hypothalamus (MH) was also lesioned separately using a nichrome electrode (0.3-mm tip exposure) with a 2.0-mA current for 20 s. Gastric emptying was measured following the orogastric infusion of a liquid test meal consisting of physiological saline (0.9% NaCl, w/v) plus phenol red dye (6 mg/dl) as a marker. Plasma glucose levels were determined after an 18-h fast before the lesion and on the 7th and 15th postoperative day. Body weight was determined before lesioning and before sacrificing the rats. The DMH-lesioned rats showed a significantly faster (P < 0.05) gastric emptying (24.7% gastric retention, N = 11) than control (33.0% gastric retention, N = 8) and sham-lesioned (33.5% gastric retention, N = 12) rats, with a transient hypoglycemia on the 7th postoperative day which returned to normal by the 15th postoperative day. In all cases, weight gain was slower among lesioned rats. Additional experiments using a smaller current to induce lesions confirmed that DMH-lesioned rats had a faster gastric emptying (25.1% gastric retention, N = 7) than control (33.4% gastric retention, N = 17) and VMH-lesioned (34.6% gastric retention, N = 7) rats. MH lesions resulted in an even slower gastric emptying (43.7% gastric retention, N = 7) than in the latter two groups. We conclude that although DMH lesions reduce weight gain, they do not produce consistent changes in plasma glucose levels. These lesions also promote faster gastric emptying of an inert liquid meal, thus suggesting a role for the DMH in the regulation of gastric motility.
Highlights
The digestive-absorptive process is dependent on the interplay between gastric emptying and small intestine movements
The effects of dorsomedial hypothalamic (DMH) nucleus lesion on body weight, plasma glucose levels, and the gastric emptying of a liquid meal were investigated in male Wistar rats (170-250 g)
We demonstrated that lesion of the paraventricular nucleus (PVN) blocked the effects of stressful stimuli on gastric emptying in rats [4]
Summary
The digestive-absorptive process is dependent on the interplay between gastric emptying and small intestine movements. Changes in gastric emptying or intestinal digestion may result in the malabsorption of nutrients leading to malnutrition [1]. Gastric emptying is regulated by motor and secretory activities of the fundus, body and antrum of the stomach [2], which may be influenced by stressful stimuli [3]. We demonstrated that lesion of the paraventricular nucleus (PVN) blocked the effects of stressful stimuli on gastric emptying in rats [4]. These observations led us to reason that other nuclei might be involved in the neuronal circuitry regulating gastric emptying. Since lesion of the dorsomedial hypothalamic (DMH) nucleus reduces weight gain and retards growth [5], we investigated the involvement of this nucleus in the control of gastric emptying
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Schedule a callMore From: Brazilian journal of medical and biological research = Revista brasileira de pesquisas medicas e biologicas
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