Keith S. Grimson

Rôle of the Sympathetic Nervous System in Experimental Neurogenic Hypertension

Recent clinical studies 1 have renewed interest in central or psychosomatic factors in essential hypertension. The sustained neurogenic hypertension in dogs described by Heymans and Bouckaert 2 seems from this point of view to afford a better experimental approach to the problem of hypertension and sympathectomy than the renal hypertension described by Goldblatt, 3 and shown to be uninfluenced by total sympathectomy. 4-7 The recent demonstration, Grimson, Bouckaert and Heymans, 8 that a sustained neurogenic hypertension of renal origin may be produced by a central reflex mechanism tends to correlate these two methods for producing experimental hypertension. The present study is based upon an effort to determine the blood pressure levels produced by section of the depressor nerves in normal dogs and compare them with the pressure levels produced by the same procedure in dogs sympathectomized with the exception of the nerve supply to the kidneys and adrenals, as well as to study the effects of renal denervation, splanchnic resection, and total para-vertebral sympathectomy on the former group. Heymans and Bouckaert 9 have shown that section of the depressor nerves produces a persistent hypertension and that total sympathectomy eliminates the hypertension. Goldblatt, Kahn, Bayless. and Simon 10 have recently failed to obtain this type of hypertension and Nowak and Walker 11 have stated that some hypertension follows depressor nerve section in sympathectomized dogs. These contraindications have further stimulated this study. In 9 dogs both carotid sinuses were excised, the left vago-sympathetic-depressor nerve was cut, and a segment of the right sympathetic depressor trunk was removed. The control blood pressures were respectively 131, 133, 134, 134, 138, 138, 144, 148 and 174.

Experimental Technic for Measuring Mean Systolic Blood Pressures During Activity, Rest, and Natural Sleep.

Blood pressures are conventionally determined in the dog either directly by a mercury or a Hamilton 1 manometer connected to a cannula or needle introduced into a large artery or indirectly by auscultation or palpation distal to a modified Riva-Rocci 2 blood pressure cuff about an extremity or a Van Leersum 3 arterial loop. The positioning or training required for these methods precludes blood pressure determinations during normal emotional and physical activity, rest, and sleep. Accordingly reported normal blood pressure values have varied significantly, A new technic for blood pressure determination that permits frequent readings during varying phases of activity or rest was therefore devised and tested. It has not to the knowledge of the authors been previously described. Healthy dogs were anesthetized and placed on one side on an operating table with the upper leg externally rotated. The lower half of the upper side of the turnk and the groin and thigh were then shaved and prepared. Employing aseptic technic, the iliac and the upper femoralartery was exposed above and below the inguinal ligament through a 3-inch incision. A 1-inch square of sterile fine mesh gauze was next placed beneath each artery. A small rubber balloon fashioned from 1/2 inch of the tin of small finger cot and attached over a short segment of 18-gague needle to a 4-fot length of fine plastic tubing was then placed above and in direct contact with each artery. Each gauze was folded about the artery and the balloon to form a cuff and sutured snugly in place. Care was taken to avoid arterial injury or constriction. Each cuff was carefully filled and tested by the introduction of sterile water under pressure. The 2 plastic tubes were then guided subcutaneously around the flank and out through a stab wound located over the first lumbar spine.

Effect of Activity, Rest, and Natural Sleep upon Blood Pressure of Renal Hypertensive Dogs

An experimental technic for measuring mean systolic blood pressure and pulse rate of dogs during activity, rest, and natural sleep has been described. 1 This technic has been applied to normal dogs and to dogs with neurogenic hypertension produced by excision of the 2 carotid sinuses, section of one vagus sympathetic depressor nerve trunk, and division of the remaining depressor nerve. 2 Variations of blood pressure were noted in both the control and the neurogenic hypertensive dogs. Blood pressures were highest during activity and standing or feeding and lowest during rest and natural sleep. The reduction of pressure of animals with neurogenic hypertension during rest or natural sleep did not reach levels comparable with those reached by normal dogs. The present experiment was undertaken to determine the effect of activity and rest upon dogs with renal hypertension produced by placing capsules about the kidney, Page. 3 Hypertension was produced in 3 dogs with normal blood pressure by placing silk capsules about both kidneys in 2 (dogs 1 and 2, Fig. 1) and plastic capsules in one (dog 3, Fig. 1). It was produced in a 4th dog by placing a silk capsule about one kidney and removing the other. Blood pressures as determined by direct arterial puncture rose to levels between 190 and 206 mm Hg during the 25 to 36 days that elapsed before the final experiment. Cuffs were then placed about the right iliac and femoral arteries and the animals were prepared for blood pressure determination according to the technic previously described. 1 After complete recovery from anesthesia blood pressures and pulse rates were recorded at frequent intervals for periods from 49 to 76 hours. The variation and the mean of readings of 3 dogs taken when they were feeding, moving about the cage, standing quietly, lying and resting, or sleeping are illustrated in Fig. 1.