Dr. Knoblich's Research Projects

Renal Effects of Electrical Stimulation of the Dorsal Spinal Column

Electrical stimulation of the dorsal spinal column is well established to improve peripheral blood flow and pain management in peripheral vascular disease. The stimulation must be applied at the site of sensory nerve entrance into the spinal column from the area affected. The same type of stimulation has been used with some success to treat angina. Our laboratory is investigating this type of stimulation on renal blood flow, urinary sodium excretion, and sympathetic tone. Anesthetized rats are subjected to dorsal spinal stimulation in the area of entry of the renal sensory nerves. Blood pressure, heart rate, renal blood flow, and renal sodium excretion are monitored.

The Effects Of Exercise on the Renin-Angiotensin-Aldosterone System

Exercise has been shown to decrease blood pressure in humans, at least in the short term (several months.) Not all mechanisms by which exercise has this blood pressure lowering effect have been determined. Angiotensin 2 is a potent vasoconstrictive agent, regulated by the kidneys. This study investigates the cardiovascular and renal responses to angiotensin 2 infusions in exercised and sedentary hypertensive and normotensive rats. Rats are assigned to an exercise or sedentary group from 5 to 12-14 weeks of age. Acute studies are performed at 12-14 weeks of age. Following anesthesia, several concentrations of angiotensin 2 are infused, and the cardiovascular and renal responses are monitored.

The Effects of Exercise on Pressure-Induced Natriuresis

This study investigates the effect of exercise on pressure-induced natriuresis hypertensive and normotensive rats. Not all mechanisms by which exercise has this blood pressure lowering effect have been determined. It is believed by some researchers that high blood pressure occurs because the kidneys do not eliminate enough sodium as blood pressure rises. Pressure-induced natriuresis refers to sodium excretion in the urine in response to a rise in blood pressure. Rats are divided into sedentary and exercise groups from 5 to 12-14 weeks of age. Acute studies are performed at 12-14 weeks of age. Blood pressure is artificially raised by ligation of several abdominal arteries, and sodium excretion is monitored in response to the rise in blood pressure.

Effects of Reduced Adrenalcortical Hormones on Blood Pressure Development, Fetal Development, and Offspring

Adrenal cortical hormones have been deemed necessary for hypertension to occur in the spontaneously hypertensive rat. However, little is known about the effect of a reduction (rather than an elimination) of these hormones and hypertension development. A surgical technique to reduce adrenal hormones to less than half the control levels has been developed. The reduction is sustained for at least 8 weeks post surgery. Currently the technique (or a sham surgery) is performed on weanling normotensive and hypertensive rats, and their cardiovascular development and weight are monitored until about 23 weeks of age.

Adrenal hormones appear to be necessary for normal fetal development. An excess of corticosterone has been implicated in certain adverse prenatal outcomes. Little is known about the effect of a reduction of adrenal hormones of fetal or offspring development. The procedure or a sham surgery is performed on adult female hypertensive and normotensive rats, which are allowed to recover, and then are mated. Fetal data is collected on day 21 of gestation (gestation is 22-23 days) including weight, litter numbers, resorption sites, and kidney and placenta weights. In addition, offspring (of other treated and sham females) are studied from 5 to 23 weeks of age, as to systolic blood pressure, heart rate, and weight gain.