Peripheral nerve conduction abnormalities precede morphological alterations in an experimental rat model of sepsis.

PURPOSE: The pathological mechanisms of critical illness polyneuropathy (CIP), an acute neuromuscular disorder, remain unknown. In this study, we evaluated nerve and vascular properties that might account for electrophysiological abnormalities, including reduced nerve conduction amplitude, in the early phase of CIP. METHODS: Rats were administered intravenous saline (C-group; n = 31) or lipopolysaccharide (3 mg/kg/day; L-group; n = 30) for 48 h. Subsequently, tracheotomy was performed and sciatic nerves exposed bilaterally. A catheter was inserted into the left internal carotid artery to measure the mean arterial pressure (MAP). Nerve conduction velocity (NCV), nerve blood flow (NBF), evoked amplitudes, chronaxie, rheobase, and the absolute refractory period (ARP) were measured from the sciatic nerves. Degeneration, myelination, and neutrophil infiltration were examined in the sciatic nerves using histology and electron microscopy. RESULTS: The NBF (C-group 25 ± 3 ml/100 g/min, L-group 13 ± 3 ml/100 g/min, p < 0.001) was lower in the L-group, but the MAP was similar between groups (C-group 119 ± 17 mmHg, L-group 115 ± 18 mmHg, p = 0.773). LPS also caused a severe reduction in amplitude (C-group 0.9 ± 0.2 mV, L-group 0.2 ± 0.1 mV, p < 0.001), while latency and NCV were not affected. Of note, response amplitudes partially recovered with an increase in stimulus intensity. LPS treatment increased the rheobase and decreased the chronaxie (rheobase: C vs L-group; 0.35 ± 0.07 vs 1.29 ± 0.66 mA, p < 0.001; chronaxie 171 ± 24 vs 42 ± 20 µs, p < 0.001), while ARP was unchanged. No primary axonal degeneration or inflammatory infiltration was observed. CONCLUSIONS: Our findings suggest that primary electrophysiological deterioration is due to threshold alterations rather than morphological alterations after 48 h of LPS treatment.

Effects of Kampo herbal medicine on plasma melatonin concentration in patients.

There are studies reporting that some natural products containing melatonin. Sleep disturbance and nocturnal polyuria are related to abnormal biorhythm. It is possible that kampo medicine may influence biorhythm. We therefore examined the symptoms and plasma melatonin of patients treated with rokumi-gan, hachimi-jio-gan, gosha-jinki-gan and seishinrenshi-in. Furthermore, the concentration of four kampo medicines and crude drugs making up these formulations were investigated. Diurnal plasma melatonin was not affected by Rokumi-gan, but tended to be lowered by treatment with hachimi-jio-gan, gosha-jinki-gan and seishinrenshi-in. Melatonin was present in several extracts from crude drugs, namely Rehmanniae radix, Moutan cortex, Cinnamomi cortex, Aconiti tuber, Plantaginis semen, Scutellariae radix and Lycii radicis cortex.