Summary
Small electrolytic lesions were placed bilaterally in the ventromedial hypothalamus of weanling male Sprague-Dawley rats to investigate the effect of lesion size and extent on changes in carbohydrate and lipid metabolism previously reported in this model of experimental obesity. Two experiments were performed. In one experiment, both small, single-focus lesions of the ventromedial hypothalamic nuclei (VMN) and larger lesions consisting of an antero-posterior sequence of three confluent electrolytic foci extending throughout the length of the VMN were found to result in increased glucose-U-C14 oxidation and increased incorporation of this metabolite into epididymal-fat-pad lipid. However, only the triple-focus lesions produced decreased palmitate-l-C14 oxidation and increased lipid percent wet weight. In a second experiment, the effects of single-focus lesions were compared with those produced by a series of three confluent lesions placed along a vertical electrode track so as to destroy more of the dorsal region of the VMN and part of the dorsomedial hypothalamic nucleus. In a third group of rats, three electrolytic foci were aligned in the mediolateral direction so as to involve the full width of the VMN and the area lateral to this nucleus. All types of lesions in the last two experiments resulted in changes comparable in nature and magnitude to those produced by the single- and triple-focus lesions in the first experiment. The findings indicate that the hypothalamic locus that must be destroyed bilaterally in order to produce the metabolic alterations in the “Weanling VMN Syndrome” is confined to the ventromedial hypothalamic nucleus.
Zusammenfassung
Wie in früheren Arbeiten gezeigt, führen experimentelle Läsionen des Hypothalamus über Anomalien im Kohlenhydrat- und Fettstoffwechsel zu Fettsucht. Bilateral wurden gezielte elektrolytische Läsionen am N. ventromedialis (VMN) des Hypothalamus abgesetzter männlicher Ratten vorgenommen, um die Auswirkungen von Größe und Ausdehung definierter Läsionen auf den Stoffwechsel zu erfassen.
In einem ersten Experiment wurde bei einer Versuchtstiergruppe bilateral jeweils eine auf den N. ventromedialis beschränkte kleine Läsion gesetzt, bei einer Gruppe drei größere Läsionen in Längsrichtung des N. ventromedialis rostrocaudal aneinandergereiht. Beide Versuchsanordnungen ergaben eine erhöhte Oxydation von Glucose-U-C14 sowie den gesteigerten Einbau dieses Metaboliten in epididymales Fettgewebe. Lediglich die dreifachen Läsionen führten zu einer Verringerung der Oxydation von Palmitat-1-C14 und zu einer Zunahme der Lipidspeicherung bezogen auf nasses Organgewicht.
In einem zweiten Experiment wurde die Wirking von bilateralen Einzelläsionen verglichen mit den Folgen je drei aneinandergereihter Läsionen in dorsoventraler Richtung mit der Zerstörung des dorsalen Abschnittes des N. ventromedialis und eines Teils des N. dorsomedialis des Hypothalamus. Bei einer weiteren Gruppe von Ratten wurden in mediolateraler Richtung hintereinander drei Läsionen gesetzt, um den N. ventromedialis in seiner ganzen Ausdehnung nach lateral auszuschalten, dazu die Region lateral des Kerngebietes. Alle diese Läsionen verursachten ähnliche Stoffwechselstörungen wie das erste Experiment.
Die Befunde weisen darauf hin, daß ausschließlich die bilaterale Zerstörung des N. ventromedialis des Hypothalamus zu den Stoffwechselstörungen führt, die als „Weanling VMN Syndrom” bezeichnet werden.
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This investigation was supported by USPHS grants HD-0331 and AM-11746, NIH, and a Veterans Administration Clinical Investigatorship (JKG).
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Bernardis, L.L., Goldman, J.K. Effect of hypothalamic lesion localization and size on metabolic alterations in weanling rat adipose tissue. J. Neuro-Viscer. Relat 32, 253–269 (1972). https://doi.org/10.1007/BF02327924
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DOI: https://doi.org/10.1007/BF02327924