Lesions of the Dorsomedial Hypothalamic Nucleus Do Not Influence the Daily Profile of Pineal Metabolism in Rats

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Abstract

The present study attempted to characterize the effects of electrolytic lesions of the hypothalamic dorsomedial nucleus on the daily profile of pineal metabolism as well as on the inhibition of pineal melatonin synthesis induced by acute light exposure during the night. Adult male Wistar rats (n = 107, 12:12 h light-dark cycle) were left intact (n = 47) or lesioned (n = 60). Lesioned rats and their respective controls were killed at six time points distributed throughout the light-dark cycle. At ZT (zeitgeber time) 18 the animals were killed either in the dark or after 15 min of light stimulation. Pineal glands were assayed using high-performance liquid chromatography with electrochemical detection (HPLC-ED). There was no difference in the amounts of pineal indoles between lesioned and control rats under any of the experimental situations tested. These results suggest that in rats, the hypothalamic dorsomedial nucleus does not participate in either the neural control of daily pineal metabolism or the nocturnal light-induced inhibition of the pineal metabolism.

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Pineal N-acetyltransferase and hydroxyindole-O-methyltransferase: control by the retinohypothalamic tract and the suprachiasmatic nucleus.

D. Klein, Jamie Moore (1979)

The visual pathway and central neural structures involved in the photic and endogenous regulation of the activity of pineal N-acetyltransferase and hydroxyindole-O-methyltransferase were investigated. The results indicate that the visual pathway regulating both enzymes is the retinohypothalamic tract, and that the inferior accessory optic tract is clearly not involved in the regulation of hydroxyindole-O-methyltransferase activity, as has been previously thought. In addition, the suprachiasmatic nucleus was found to be necessary for the generation of a rhythm in N-acetyltransferase activity in blinded animals, and to be responsible for the tonic elevation of hydroxyindole-O-methyltransferase activity in blinded animals. Finally, it was concluded that the rapid and large daily changes in N-acetyltransferase activity seen in a normal lighting cycle and the much slower and smaller changes in hydroxyindole-O-methyltransferase activity seen only after weeks in constant lighting conditions are mediated by the same neural tract; the different time courses of the effects of environmental lighting may be explained on the basis of different intracellular regulatory mechanisms.

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The course of paraventricular hypothalamic efferents to autonomic structures in medulla and spinal cord.

P.G.M. Luiten, G.J. ter Horst, H Karst … (1985)

By application of the anterograde transport technique of Phaseolus vulgaris leuco-agglutinin the descending autonomic projection of the paraventricular hypothalamic nucleus was investigated. The Phaseolus lectin technique allowed the detection of the cells of origin in the paraventricular PVN, the precise position of two distinct descending axon pathways and the detailed morphology of terminal structures in midbrain, medulla oblongata and spinal cord.

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The projections of the dorsomedial hypothalamic nucleus in the rat.

G.J.Ter Horst, P.G.M. Luiten (1986)

The dorsomedial hypothalamic nucleus (DMH) output pathways are revealed by using autoradiographic tracing of tritium labeled Leucine and by the recently introduced Phaseolus vulgaris leuco-agglutinin immunocytochemical method. Terminal labeling appears in the dorsal motor nucleus of the vagus, nucleus ambiguus and in the parvocellular reticular formation at the lower medullary level. Mesencephalic labeling is found in the periaqueductal gray at the level of the oculomotor nucleus. In the hypothalamus labeled terminal boutons are identified in the lateral and ventromedial hypothalamic nuclei but also in the parvocellular paraventricular nucleus. Furthermore, the circumventricular organs are found to receive a dense DMH input, particularly the organum vasculosum of the lamina terminalis and the subfornical organ. These findings are discussed in relation to the dorsomedial nucleus involvement in the control of feeding and pancreatic hormone release. It appears that the DMH participates in this control via descending pathways to the preganglionic pancreas innervating neurons but also via a neuroendocrine route. The latter connection is indicated by terminal labeling in the parvocellular paraventricular nucleus in the area that contains the corticotropin-releasing factor positive cells.

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Author and article information

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Journal ID (publisher-id): NEN

Journal ID (nlm-ta): Neuroendocrinology

Journal ID (doi): 10.1159/issn.0028-3835

Title: Neuroendocrinology

Publisher: S. Karger AG

ISSN (Print): 0028-3835

ISSN (Electronic): 1423-0194

Publication date Subscription-year: 2001

Publication date (Print): February 2001

Publication date (Electronic): 23 February 2001

Volume: 73

Issue: 2

Pages: 123-128

Affiliations

^aDepartment of Physiology and Biophysics, Institute of Biomedical Sciences, University of São Paulo, and ^bLaboratory of Pharmacology, Institute Butantan, São Paulo, Brazil

Article

Publisher ID: 54628 Other ID: Neuroendocrinology 2001;73:123–128

DOI: 10.1159/000054628

PubMed ID: 11244299

SO-VID: 034a6fbe-9895-4b24-a2b8-ad8de9e3ac00

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Lesions of the Dorsomedial Hypothalamic Nucleus Do Not Influence the Daily Profile of Pineal Metabolism in Rats

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Karger: Endocrinology

Most cited references 10

Pineal N-acetyltransferase and hydroxyindole-O-methyltransferase: control by the retinohypothalamic tract and the suprachiasmatic nucleus.

The course of paraventricular hypothalamic efferents to autonomic structures in medulla and spinal cord.

The projections of the dorsomedial hypothalamic nucleus in the rat.

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