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      Diurnal Variation in the Release of Alpha-MSH from Rat Hypothalamus and Pituitary

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          Release of α-MSH from rat hypothalamic slices was characterized with respect to ionic requirements and possible diurnal variations using a sensitive radioimmunoassay. Addition of 47 mM KCl to the superfusion medium resulted in a twofold increase in α-MSH release compared to spontaneous release. Removal of calcium from the superfusion medium abolished the potassium-evoked release of α-MSH. This supports the concept that α-MSH functions as a neurotransmitter or neuromodulator in the hypothalamus. Both spontaneous and potassium-induced α-MSH release were related to diurnal variation. Marked release from the slices was observed at 10.10 h, corresponding to a peak in the α-MSH concentration in the hypothalamus [18] and to a low level of α-MSH in the blood. Contrarily, no significant release from the hypothalamus was obtained at 17.00 h when hypothalamic α-MSH content was low, but blood levels exhibited a peak. These findings suggest that there are differences in the regulation of the α-MSH from the pituitary and that in the hypothalamus.

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          Author and article information

          S. Karger AG
          26 March 2008
          : 33
          : 5
          : 284-287
          Institutes of Pharmacology and Brain Research, University of Zurich, and Institute of Molecular Biology, Federal Institute of Technology, Zurich, Switzerland
          123246 Neuroendocrinology 1981;33:284–287
          © 1981 S. Karger AG, Basel

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          Pages: 4
          Original Paper


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