抄録
The cardiovascular responses to pressor, de-pressor agents and carotid occlusion in the Spontaneously Hypertensive Rats (OKAMOTO and AOKI) were investigated. Spontaneously hypertensive rats were divided into 3 groups, i. e., the pre-hypertensive or transitional stage (Sy ; 40-60 days old), the earliest hypertensive stage (Sp ; 60-110 days old) and the early hypertensive stage (Sa; 130-210 days old), and were compared with acute and chronic renal infarction hypertension (Ry, Ra), acute constricted renal artery hypertension (Rg) and normotensive controls at the corresponding age, respectively. Direct blood pressure was recorded manometrically on kymograph under chloralose (40 mg/kg, intravenous administration) anesthesia and all pressor or depressor agents were administered intravenously and the following results were obtained. 1) Spontaneously hypertensive rats (Sp, Sa) after the development of hypertension, which seemed somewhat easily depressed by general anesthesia maintained hypertensive blood pressure level under chloralose (40mg/ kg) anesthesia. 2) Response to adrenalin (5γ/kg) was slightly decreased in spontaneously hypertensive rats (Sy, Sa), but response to noradrenalin (5γ/kg) showed an increasing tendency in spontaneously hypertensive rats in the early stage (Sa) as well as in chronic renal hypertensive rats (Ra). 3) Pressor response induced by bilateral carotid occlusion for 20 seconds was significantly increased in spontaneously hypertensive rats (Sy, Sa) and renal hypertensive rats (Ry, Ra) in comparison with normotensive controls. Spontaneously hypertensive rats in the pre-hypertensive or transitional stage (Sy) did not show a significantly increased carotid occlusion reflex until atropine (2mg/kg) was administered. 4) The depressor effect of regitine (0.6mg/kg) in spontaneously hypertensive rats in the pre-hypertensive stage (Sy) was almost the same as that in controls. Spontaneously hypertensive rats in the early stage (Sa) showed nearly the same increased response as chronic renal hypertensive rats (Ra) but a significantly increased response in comparison with acute renal hypertensive rats (Ry). 5) The stable pressure level after hexamethonium (20mg/kg) administration was significantly lower in spontaneously hypertensive rats in the earliest hypertensive stage (Sp) than in acute renal hypertensive rats with constricted renal arteries (Rg). 6) The effect of acetylcholine (2γ/kg) on blood pressure was significantly increased in spontaneously hypertensive rats in the pre-hypertensive or transitional stage (Sy) and in acute renal hypertensive rats (Ry) as compared with controls. 7) These results suggested the probable participation of neural fractors in the development of spontaneous hypertension. Differences between spontaneous and renal hypertension as well as the similarity of spontaneous hypertension to human essential hypertension in early stage were also discussed.
