Functional Correlations Between Hypothalamus and Hepatic Metabolism

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The actions of hepatic sympathetic nerves on glycogenolysis were studied in rat livers perfused in situ without recirculation. A bipolar platinum electrode was placed around the hepatic hilus and rectanglar monophasic impulses (20V, 2ms, 20Hz) were applied. In female rat livers both phenylephrine and isoproterenol stimulated glycogenolysis, but the effects of nerve stimulation (NS) were completely abolished by phentolamine. Mepacrine, a phospholipase A_2 inhibitor, markedly suppressed glycogenolysis by NS without affecting norepinephrine overflow. It had no effect, however, on glycogenolysis by phenylephrine. Prostaglandin F_<2alpha> (PGF_<2alpha>) mimicked the effect of NS but phentolamine had no effect on PGF_2. These results suggest that in rat livers eicosanoids produced via an alpha-receptor mediated function play a vital role in the activation of glycogenolysis by NS. Since it has been reported that zymosan (Cell wall particles from yeast) is selectively taken up by kupffer cells and that zymosan is able to stimulate production of eicosanoids, the experiments were carried out to examine the direct effects of sympathetic nerve stimulation and zymosan on glycogenolysis in perfused liver isolated from rats exposed to cold. The results suggest that hepatic nerve may regulate the arachidonic pathways in kupffer cells during cold exposure.