Epinephrine: a mediator of plasma glycerol elevation by hypothalamic stimulation.

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Abstract
Electrical stimulation of the ventromedial hypothalamus [VMH] of the adult rabbit elevates the plasma glycerol concentration. Which catecholamine from the adrenal mddulla of the rabbit participates in this plasma glycerol elevation was studied. The unstimulated plasma epinephrine [E] and norepinephrine [NE] concentrations of the adrenalectomized rabbit were 8 and 270% of those of the normal animal, respectively. The unstimulated plasma E and NE concentrations of the chemically sympathectomized animal were 220 and 41%, respectively. Electrical stimulation of the VMH of the normal and sympathectomized animals increased plasma E 6- to 7-fold and glycerol concentrations 4-fold but increased plasma NE concentrations only slightly. Adrenalectomy nearly abolished both plasma glycerol and E elevations produced by stimulation of the VMH. The calculated increments in E inflow rates during VMH stimulation of the normal and sympathectomized animals were 86 .+-. 8 and 208 .+-. 17 ng/kg per min, whereas the NE inflow rates were 13 .+-. 2 and 20 .+-. 4 ng/kg per min. Infusions of E and NE at less than 40 and 600 ng/kg per min did not elevate plasma glycerol concentration, whereas E infusions at more than 80 ng/kg per min increased the plasma glycerol concentration to the same extent as electrical stimulation. These results suggest that the plasma glycerol elevation produced by electrical stimulation of the VMH is mediated by E from the adrenal medulla rather than by NE.