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Relationship between hypothalamic noradrenergic activity and the sympathetic activity in interscapular brown adipose
M Gotoh1, G A Smythe, A Iguchi
1Garvan Institute of Medical Research, St. Vincent's Hospital, Sydney, Australia.
Abstract:
Noradrenaline (NA) activities in both hypothalamus and interscapular brown adipose tissue (IBAT) were simultaneously assessed before and after cold-swim stress in rats. The technique of gas chromatography-mass spectrometry was employed for the analysis of NA and its primary neuronal metabolite, 3,4-dehydroxy-phenylethylenglycol (DHPG), and the ratio of DHPG to NA was used as an index of NA activity. The ratios of DHPG/NA in both hypothalamus and IBAT were significantly elevated 5 and 20 min after cold-swim stress. Moreover, we found that there is a highly significant positive relationship between the hypothalamic DHPG/NA ratio and the ratio of DHPG/NA in IBAT (r = 0.872, p less than 0.0001). This observation strongly supports the concept in which hypothalamic NA neurons play an important role in modulating the sympathetic outflow.