Sural Nerve Perfusion in Mice

Peripheral nerve function is metabolically demanding and nerve energy failure has been implicated in the onset and development of diabetic peripheral neuropathy and neuropathic pain conditions. Distal peripheral nerve oxygen supply relies on the distribution of red blood cells (RBCs) in just a few, nearby capillary-sized vessels and is therefore technically challenging to characterize. We developed an approach to characterize distal sural nerve hemodynamics in anesthetized, adult male mice using in vivo two-photon laser scanning microscopy. Our results show that RBC velocities in mouse sural nerve vessels are higher than those previously measured in mouse brain, and are sensitive to hindlimb temperatures. Nerve blood flow, measured as RBC flux, however, was similar to that of mouse brain and unaffected by local temperature. Power spectral density analysis of fluctuations in RBC velocities over short time intervals suggest that the technique is sufficiently sensitive and robust to detect subtle flow oscillations over time scales from 0.1 to tens of seconds. We conclude that in vivo two-photon laser scanning microscopy provides a suitable approach to study peripheral nerve hemodynamics in mice, and that local temperature control is important during such measurements.

025 The utility of nerve blood flow in the assessment of peripheral neuropathy

IntroductionAnimal and human studies of diabetes have shown significant alterations in nerve blood flow (NBF), which may also play a role in the development of neuropathy. However, the non-invasive assessment of NBF in human subjects has remained elusive until the recent technological advancements in ultrasound (US) technology. We undertook sonographic assessment of NBF in 75 patients with type 2 diabetes and correlated the findings with neuropathy severity scores and electrophysiological parameters.MethodsBlinded median and tibial nerve ultrasound scans were performed at non-entrapment sites using a high-resolution linear probe. NBF was quantified using power Doppler techniques to obtain the vessel score (VSc) and maximum perfusion intensity (MPI). Routine nerve conduction studies were performed, and neuropathy severity was assessed using the total neuropathy score (TNS). Aged- and gender-matched controls were enrolled.ResultsDiabetic nerves had higher rates of NBF detection (28%) compared to the control group (p<0.0001). Significant correlations were found between NBF parameters and nerve size (p<0.001), reported sensory symptoms (p<0.05) and neuropathy severity scores (p<0.001). The cohort with diabetes had significantly larger median (8.5 ± 0.3 mm2 vs. 7.2 ± 0.1 mm2, p<0.05) and tibial (18.0 ± 0.9 mm2 vs. 12. 8 ±0.5 mm2, p<0.05) nerves compared to controls.ConclusionsPeripheral nerve hypervascularity is detectable by US in moderate to severe diabetic neuropathy with prominent sensory dysfunction. Consistent with previous studies, the sonographic detection of NBF is a pathological finding.

Gentiopicroside Ameliorates Diabetic Peripheral Neuropathy by Modulating PPAR- Γ/AMPK/ACC Signaling Pathway

Background/Aims: Gentiopicroside is promising as an important secoiridoid compound against pain. The present study aimed to investigate the analgesic effect and the probable mechanism of Gentiopicroside on Diabetic Peripheral Neuropathy (DPN), and to figure out the association among Gentiopicroside, dyslipidemia and PPAR- γ/AMPK/ACC signaling pathway. Methods: DPN rat models were established by streptozotocin and RSC96 cells were cultured. Hot, cold and mechanical tactile allodynia were conducted. Blood lipids, nerve blood flow, Motor Nerve Conduction Velocity (MNCV) and Sensory Nerve Conduction Velocity (SNCV) were detected. Gene and protein expression of PPAR- γ/AMPK/ACC pathway was analyzed by reverse transcription-quan titative polymerase chain reaction (RT-qPCR) and Westernblot. Besides, PPAR-γ antagonist GW9662 and agonist rosiglitazone, AMPK antagonist compound C and activator AICAR as well as ACC inhibitor TOFA were used to further confirm the relationship between PPAR-γ and AMPK. Results: The results demonstrated that Gentiopicroside markedly ameliorated hyperalgesia with prolonged paw withdrawal latency to heat and cold stimuli and fewer responses to mechanical allodynia compared with DPN model group. Gentiopicroside regulated dyslipidemia, enhanced nerve blood flow and improved MNCV as well as SNCV. Gentiopicroside suppressed ACC expression through the activation of AMPK and PPAR-γ mediated the activation of AMPK and subsequent inhibition of ACC expression. Conclusion: In conclusion, the present study demon strated that Gentiopicroside exerted nerve-protective effect and attenuated experimental DPN by restoring dyslipidmia and improved nerve blood flow through regulating PPAR-γ/AMPK/ACC signal pathway. These results provided a promising potential treatment of DPN.

Effects of Wrist Posture and Fingertip Force on Median Nerve Blood Flow Velocity

Purpose. The purpose of this study was to assess nerve hypervascularization using high resolution ultrasonography to determine the effects of wrist posture and fingertip force on median nerve blood flow at the wrist in healthy participants and those experiencing carpal tunnel syndrome (CTS) symptoms. Methods. The median nerves of nine healthy participants and nine participants experiencing symptoms of CTS were evaluated using optimized ultrasonography in five wrist postures with and without a middle digit fingertip press (0, 6 N). Results. Both wrist posture and fingertip force had significant main effects on mean peak blood flow velocity. Blood flow velocity with a neutral wrist (2.87 cm/s) was significantly lower than flexed 30° (3.37 cm/s), flexed 15° (3.27 cm/s), and extended 30° (3.29 cm/s). Similarly, median nerve blood flow velocity was lower without force (2.81 cm/s) than with force (3.56 cm/s). A significant difference was not found between groups. Discussion. Vascular changes associated with CTS may be acutely induced by nonneutral wrist postures and fingertip force. This study represents an early evaluation of intraneural blood flow as a measure of nerve hypervascularization in response to occupational risk factors and advances our understanding of the vascular phenomena associated with peripheral nerve compression.