Effects of Immunosympathectomy on Development of High Blood Pressure in Genetically Hypertensive Rats

Newborn male rats from the New Zealand colony with genetic hypertension (hypertensive rats) and from a normotensive colony (controls) were immunosympathectomized by injections of antiserum to nerve growth factor. Blood pressure of immunosympathectomized hypertensive rats aged 63 days (128±2 mm Hg) was significantly less (P<.001) than that of untreated hypertensive rats (176±3 mm Hg) of the same age. Pressure of immunosympathectomized controls aged 63 days (107±2 mm Hg) was significantly less (P<.001) than that of untreated controls (126±1 mm Hg) at the same age. Pressure thereafter remained near these levels. In immunosympathectomized rats, ganglion blockade with supramaximal doses of hexamethonium still induced a lar51ge fall in pressure which was significantly lower than in untreated rats. The combination of immunosympathectomy and hexamethonium brought the pressure of hypertensive rats and controls down to the same level (68 mm Hg). The pressor response to intravenous norepinephrine was greater in immunosympathectomized than in untreated rats. Resistance to flow in perfused mesenteric arteries from immunosympathectomized hypertensive rats was significantly less (P<.05) than in arteries from untreated hypertensive rats. Hearts of immunosympathectomized hypertensive rats were significantly lighter (P<.01) than those of untreated hypertensive rats. Heart rates of hypertensive or control rats were not altered by immunosympathectomy.