These alterations include increases in sensitivity to contractile agonists and altered membrane ionic permeabilities. Jones and Miller 2 have proposed that these changes in vascular smooth muscle function in hypertension may parallel the difference between tonic and phasic types of smooth muscle. Indeed, isolated blood vessels from hypertensive animals often exhibit spontaneous rhythmic contractions. 3 Previous experiments in our laboratory 4 have identified an unusual contractile response in isolated tail arteries from spontaneously hypertensive stroke prone
SUMMARY Inflatable suits were constructed for lower body compression in pigs and dogs. The suit for pigs encompassed hindquarters and part of the abdomen, and the smaller suit for dogs compressed only the hindquarters, leaving free the abdominal cavity. In conscious, diazepam-pretreated pigs, the compression lasted 30 minutes; during that period the blood pressure increased 50/38 mm Hg over the baseline. In chloralose-anesthetized dogs, the compression was extended to 3 hours; the blood pressure increase was 44/53 mm Hg. Blood pressure fell to the baseline immediately after decompression in both animals. In both species the substantial blood pressure increase was due to an increase of vascular resistance; this did not induce the expected baroreceptor-mediated bradycardia. In dogs, the blood pressure increase was accompanied by a large increase of plasma norepinephrine (from 179 to 975 pg/ml). To test whether the increase of vascular resistance reflected the mechanical compression of the vessels under the suit, animals were pretreated with trimethaphan. In pigs the trimethaphan substantially decreased the vascular resistance and the blood pressure response. This indicated that a portion of the vasoconstriction occurred in areas outside the suit. Lower body compression is a new model to cause prolonged blood pressure elevation by noninvasive and nonpharmacologic means. The mechanism of the blood pressure elevation requires further investigation. (Hypertension 4: 782-788, 1982) KEY WORDS • cardiac output • hemodynamics • right atrial pressure • norepinephrine * vascular resistance • trimethaphan A S a follow-up to our work on the role of cardiac receptors in the regulation of renin release, 1 we searched for a practical way to translocate blood from the lower part of the body to the cardiopulmonary region. A suit for lower body compression of pigs was constructed. It soon became evident that external compression of the lower body induces a prolonged increase of blood pressure. This blood pressure elevation became the main focus of our research. A smaller suit that compresses only the hindquarters but not the abdomen of dogs was then constructed to further investigate this blood pressure response. Large and prolonged blood pressure elevations were also seen in dogs.The hemodynamic characteristics of the sustained blood pressure response to the lower body compression in pigs and to hindquarter compression in dogs are the subject of this report. Material and Methods PigsNine young male Yorkshire pigs weighing between 30 and 60 kg were used in this study. Aortic pressure was measured via a Herd-Barger catheter 2 inserted in the thoracic part of the descending aorta, and central venous pressure was measured through a similar catheter with its tip placed at the confluence of the superior and inferior vena cavae. Both pressures were monitored by means of Statham strain gauges and recorded on a Grass polygraph. Relative cardiac output was measured with an electromagnetic flow probe (Zapeda Instruments, Seattle, Washing...
We have developed and employed a stereotaxic coordinate system for the pig brain based on eternal skull landmarks. Sagittal, coronal, and horizontal planes were defined. Based on histological maps and ventricular casts, the coordinates for locating the lateral ventricles were described. Guide tubes leading to the lateral ventricles have been chronically implanted. This access route to the ventricular system has been used for stimulation of the dipsogenic response with angiotensin and for withdrawal of cerebrospinal fluid. Solved and unsolved problems arising with these procedures have been defined.
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