Electrophysiological investigations in mice, particularly with altered myelination, require reference data of the nerve conduction velocity (CV). CVs of different fibre groups were determined in the hindlimb of anaesthetized adult mice. Differentiation between afferent and efferent fibres was performed by recording at dorsal roots and stimulating at ventral roots, respectively. Correspondingly, recording or stimulation was performed at peripheral hindlimb nerves. Stimulation was performed with graded strength to differentiate between fibre groups. CVs of the same fibre groups were different in different nerves of the hindlimb. CVs for motor fibres were for the tibial nerve (Tib) 38.5±4.0 m/s (Aγ: 16.7±3.0 m/s), the sural nerve (Sur) 39.3±3.1 m/s (12.0±0.8 m/s) and the common peroneal nerve (Per) 46.7±4.7 m/s (22.2±4.4 m/s). CVs for group I afferents were 47.4±3.1 m/s (Tib), 43.8±3.8 m/s (Sur), 55.2±6.1 m/s (Per) and 42.9±4.3 m/s for the posterior biceps (PB). CVs of higher threshold afferents, presumably muscle and cutaneous, cover a broad range and do not really exhibit nerve specific differences. Ranges are for group II 22-38 m/s, for group III 9-19 m/s, and for group IV 0.8-0.9 m/s. Incontrovertible evidence was found for the presence of motor fibres in the sural nerve. The results are useful as references for further electrophysiological investigations particularly in genetically modified mice with myelination changes., H. Steffens, P. Dibaj, E. D. Schomburg., and Obsahuje seznam literatury
During controlled ischaemia (aortal snare occlusion) of the lumbar spinal cord, microcirculatory (laser-Doppler flowmetry) and segmental neurophysiological parameters (monosynaptic reflexes, polysynaptic reflexes, cord dorsum potential = CDP) as well as interstitial concentrations of adenosine and serotonin (5-HT) were determined in the grey matter using the microdialysis/HPLC method. Ischaemic periods of 1-7 min with a residual blood flow in the lumbar spinal cord of 10-30 % of the preischaemic control blood flow caused a blockade of spinal pathways and an increase of concentrations of interstitial adenosine and 5-HT. This increase started immediately after the initiation of the ischaemic period and reached a maximum at the end or shortly after the end of the ischaemic period during postischaemic hyperaemia. A close correlation between the duration of ischaemia and the interstitial concentration of adenosine and 5-HT was not found. Repetition of ischaemic periods in an experiment did not lead to an extracellular accumulation or an exhaustion of the release of 5-HT, whereas some indication was found for an exhaustion of adenosine release. The course of the increase of interstitial adenosine and 5-HT was partly found to correlate to the loss and recovery of the CDP following ischaemia. The concentrations usually reached control levels before spinal reflexes reappeared. The highly dynamic changes in concentrations of adenosine and 5-HT in the extracellular space of the spinal cord during and after short-term ischaemia revealed some relation to the time course of recovery of segmental spinal functions by reflecting the course of spinal neuronal metabolism.
The role of L-DOPA in spinal nociceptive reflex activity has been re-evaluated. In high spinal ca ts, with supraspinal loops being excluded, the onset of reflex facilitation induced by noxious radiant heat is delayed after injection of L-DOPA by 4 to 10 s, i.e. the early component of nociceptive reflex facilitation is blocked, while the late component persisted. Further investigations have shown that the early component of reflex facilitation induced by noxious radiant heat is mediated by Aδ-fibres and the late component by C-fibres. Therefore, it can be assumed that L-DOPA, like opioids, preferentially blocks the transmission in nociceptive reflex pathways from Aδ-fibres., E. D. Schomburg, P. Dibaj, H. Steffens., and Obsahuje bibliografii a bibliografické odkazy