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Neuroendocrinology Letters incl. Psychoneuroimmunology & Chronobiology

Neuroendocrinology Letters incl. Psychoneuroimmunology & Chronobiology, Research -- Original Article
ISSN 0172–780X Copyright © 2000 Neuroendocrinology Letters

NEL VOL. 21 No. 4
ORIGINAL ARTICLE

2000; 21:307–312


Daytime pineal gland activation in rats with colon tumors induced by 1,2-dimethylhydrazine
by Dmitrii A. Sibarov, Rimma I. Kovalenko, Vladimir N. Anisimov & Alexander D. Nozdrachev

Keywords:
pinealocytes, colon tumor, 1.2-dimethylhydrazine, electrical activity, secretion, melatonin

Abstract

OBJECTIVES: Intact rats and rats with 1,2-dimethylhydrazine induced tumors of large intestine were used in experiments. Previously, blood melatonin concentration in these tumor-bearing rats was shown to increase at night, but not in the daytime. METHODS: The extracellular microelectrode registration of rat daytime pineal gland activity was performed.

RESULTS: The existence of different types of pinealocytes in the pineal gland was confirmed. Tumor-bearing rats, in comparison to intact, demonstrated higher spike frequency due to cells switching from regular to pattern (4–6 times gain) activity and appearance of “fast” cells (>5Hz frequency).

CONSLUSIONS: The literature about pinealocytes points to the correlation between electrical and secretory processes in pinealocytes; thus we suppose the groups of interacting cells, detected in tumor-bearing rats, to reflect cascade cells activation while pineal gland secretion increases. The results indicate, that in the daytime pinealocytes are secreting substances (not melatonin) in dependence with hormonal background.