The relationship between blood pressure and sciatic nerve blood flow velocity in rats with insulin-treated experimental diabetes

Abstract

Peripheral nerve blood flow (NBF) does not autoregulate but, instead, responds passively to changes in mean arterial pressure (MAP). How this relationship is impacted by insulin-treated experimental diabetes (ITED) is unknown. We tested the hypothesis that ITED will reduce NBF across a range of MAP in Sprague Dawley rats. Following 10 weeks of control or ITED conditions, conscious MAP (tail-cuff) was measured, and under anaesthesia, the MAP (carotid artery catheter, pressure transducer) and NBF (Doppler ultrasound, 40 MHz) responses to sodium nitroprusside (60 µg/kg) and phenylephrine (12 µg/kg) infusion were recorded (regression equations for MAP vs NBF were created for each rodent). Thereafter, motor nerve conduction velocity (MNCV) and nerve vascularization (haematoxylin and eosin stain) were determined. Conscious MAP was higher and MNCV was lower in the ITED group (p < 0.01). In response to drug infusions, the ΔMAP and ΔNBF were similar between groups (p ≥ 0.18). Estimated conscious NBF (based on substituting conscious MAP values into each individual regression equation) was greater in the ITED group (p < 0.01). Sciatic nerve vascularization was similar between groups (p ≥ 0.50). In contrast to the hypothesis, NBF was not reduced across a range of MAP. In spite of increased estimated conscious NBF values, MNCV was reduced in rats with ITED.

High Intensity Aerobic Exercise Training Improves Deficits of Cardiovascular Autonomic Function in a Rat Model of Type 1 Diabetes Mellitus with Moderate Hyperglycemia

“…A light plane anesthesia 0.5–1.2 g/kg has been shown to maintain the integrity of the cardiovascular system, where higher doses of urethane (above 1.5 g/kg) can produce hypotension and bradycardia, as well as high rates of mortality [ 91 , 92 ]. In the current study we used a minimal dose of 25 mg/kg, which was reported in previous studies by our laboratory to have little influence on neurovascular blood flow measures [ 93 – 95 ]. That being said, it cannot be determined to what extent, if at all, the autonomic nervous system was augmented by the urethane-chloralose treatment in comparison to conscious animals.…”

Insulin‐Stimulated Bone Blood Flow and Bone Biomechanical Properties Are Compromised in Obese, Type 2 Diabetic OLETF Rats

“…In particular, the hemodynamic response to insulin is impaired in T2D . This impaired hemodynamic response to insulin has been observed in numerous tissues, including intestine, brain, nerve, and muscle, but, to our knowledge, has not been investigated in bone. In the vascular endothelium, insulin activation of the pI3/Akt pathway promotes vasodilation mediated by endothelial‐nitric oxide synthase (eNOS) and reduces synthesis of deleterious adhesion molecules (eg, vascular cell adhesion molecule 1 [VCAM‐1]).…”