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Somatosympathetic reflexes were studied in young hyperinsulinemic, insulin-resistant (Zucker fatty) rats (ZFR) and a related control (Zucker lean) strain (ZLR). Glucose metabolism was characterized by minimal model analysis of intravenous glucose tolerance test data. Seven-week-old ZFR (n = 18) and ZLR (n = 17) were studied under pentobarbital anesthesia. Mean body weight and plasma glucose and insulin concentration were significantly greater (P < 0.05) in ZFR than in ZLR, whereas basal values of mean arterial pressure (MAP) and heart rate (HR) were not significantly different. Increments of MAP ([DELTA]MAP) and HR ([DELTA]HR) elicited by electrical stimulation of the sciatic nerve (5-s trains of 100 pulses, 0.5-ms pulse duration, 100- to 400-[micro]A pulse intensity) were significantly higher (ANOVA, P < 0.05) in ZFR at each level of stimulus intensity. Regression analysis showed a linear increase in [DELTA]MAP and [DELTA]HR with increasing sciatic nerve stimulus intensity. Pressor responses to phenylephrine after ganglionic blockade demonstrated that vascular reactivity to adrenergic stimulation is not increased in ZFR compared with ZLR. Thus this factor does not contribute to enhancement of somatosympathetic reflexes observed in this strain. Insulin sensitivity in ZFR was one-fourth (P < 0.05) that in ZLR. These results suggest that stronger sympathetic nervous reactivity in ZFR is associated with a severe insulin-resistant state before the onset of hypertension and support the hypothesis that insulin-mediated stimulation of the sympathetic nervous system is involved in the development of cardiovascular diseases related to alterations of glucose metabolism. sympathetic nervous activity; minimal model analysis; glucose kinetics; hypertension doi:10.1152/ajpregu.00644.2005

The incorporation of a pressure-dependent compliance in the three-element windkessel model (model A) of the systemic arterial system was evaluated to determine the accuracy of the linear model. Comparison of model A with nonlinear versions of the three-element windkessel model (model B1 and B2) indicated the improved data fit due to constant pressure-dependent compliance in model A. Furthermore, model A provided more accurate parameter estimates compared to models B1 and B2.

Open-loop experimental studies of the relationship between mean systemic arterial pressure (SAP) and mean baroreceptor pressure (BP) reveal that analytical data on SAP-BP and open loop gain (G)-BP curves derived from logistic function (LF) and normal-cumulative distribution function (CDF) are identical. Approximations of SAP-BP data using third-order polynomials have to be avoided for quantitative assay SAP-BP curves.

The T-tube arterial model, equipped with the potential to accurately regenerate pressure and flow waves in the ascending aorta and proximal descending aorta, is utilized to determine descending thoracic aortic compliance in anesthetized open-chest dogs. The end of the body tube displays features associated with the branching site of the abdominal aorta. Aortic pulse wave velocity measurements, computed from the calculated pressure in ascending and abdominal aorta, yield the corresponding length of the body tube. Compliance of the body tube average corresponds to the descending thoracic aortic compliance.