Summary
Bilateral electrolytic or sham-lesions of the ventromedial nuclei of the hypothalamus
(VMH) were performed on fasting (prior to and after the lesion) ether anesthetized
rats. Post-operatively (2 hours), sham-operated rats were either offered an oral glucose
solution or were submitted to an intravenous glucose injection or were left undisturbed;
lesioned rats were offered an oral glucose load or were submitted to an intravenous
glucose injection. Three hours later, the insulin response to an intravenous glucose
load was tested in all rats. No significant difference could be detected between the
results obtained in the three subgroups of sham-operated rats. By contrast, the VMH
lesioned rats exhibited a differential response according to the post-lesion treatment.
In lesioned rats, given an intravenous glucose injection in the immediate post-lesion
period, the tested insulin response was not significantly different from the response
of the controls. When lesioned animals were allowed to taste and ingest as little
as 0.5 g glucose, the tested insulin response was greatly enhanced. It is concluded
that an oral intake is a prerequisite to the induction of the insulin hyper-responsiveness
characteristic of fed VMH lesioned rats and that a 0.5 g glucose oral intake is sufficient.
Key-Words
Ventromedial Hypothalamic Lesion (VMH)
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Rat
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Insulin Hyper-Responsiveness
