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C Fibres (c + fibre)
Selected AbstractsPartial reversal of conduction slowing during repetitive stimulation of single sympathetic efferents in human skinACTA PHYSIOLOGICA, Issue 3 2004M. Campero Abstract Aims:, To describe and identify the function of a class of human C fibre with an unusual response to repetitive electrical stimulation. Other C fibres slow progressively at 2 Hz (type 1), reach a latency plateau (type 2) or hardly slow at all (type 3). Methods:, C fibres innervating hairy skin were recorded by microneurography in the superficial peroneal nerves of 19 healthy volunteers. Baseline electrical stimulation of the skin was at 0.25 Hz, and activity-dependent slowing recorded during stimulation at 2 Hz for 3 min and after a 3-min pause in stimulation. Results:, In 41 units, there was a partial recovery of latency during repetitive stimulation. These were classified as ,type-4' units, and identified as sympathetic efferents, since they exhibited spontaneously activity, which was enhanced by manoeuvres that increase sympathetic outflow (15 of 16 cases) and/or suppressed by a proximal anaesthetic block (eight of eight cases). The peak slowing during 2 Hz trains averaged 6.47 ± 2.06% (mean ± SD, n = 41), but after 3 min the slowing had reduced to 4.90 ± 2.20%, which was less than in all type 1 (nociceptor) fibres but similar to that in type 2 (cold) fibres. Compared with cold fibres, type-4 sympathetic fibres slowed more after the first 10 impulses at 2 Hz (2.57 ± 0.45%) and also after a pause in stimulation (1.66 ± 0.51%). Conclusions:, The distinctive activity-dependent slowing profiles of these type-4 sympathetic C units may help identification in vitro, and suggest that hyperpolarization-activated channels have a particularly prominent role in the axonal membrane. [source] The expression of vesicular glutamate transporters VGLUT1 and VGLUT2 in neurochemically defined axonal populations in the rat spinal cord with emphasis on the dorsal hornEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 1 2003A. J. Todd Abstract Two vesicular glutamate transporters, VGLUT1 and VGLUT2, have recently been identified, and it has been reported that they are expressed by largely nonoverlapping populations of glutamatergic neurons in the brain. We have used immunocytochemistry with antibodies against both transporters, together with markers for various populations of spinal neurons, in an attempt to identify glutamatergic interneurons in the dorsal horn of the mid-lumbar spinal cord of the rat. The great majority (94,100%) of nonprimary axonal boutons that contained somatostatin, substance P or neurotensin, as well as 85% of those that contained enkephalin, were VGLUT2-immunoreactive, which suggests that most dorsal horn neurons that synthesize these peptides are glutamatergic. In support of this, we found that most somatostatin- and enkephalin-containing boutons (including somatostatin-immunoreactive boutons that lacked calcitonin gene-related peptide and were therefore probably derived from local interneurons) formed synapses at which AMPA receptors were present. We also investigated VGLUT expression in central terminals of primary afferents. Myelinated afferents were identified with cholera toxin B subunit; most of those in lamina I were VGLUT2-immunoreactive, whereas all those in deeper laminae were VGLUT1-immunoreactive, and some (in laminae III,VI) appeared to contain both transporters. However, peptidergic primary afferents that contained substance P or somatostatin (most of which are unmyelinated), as well as nonpeptidergic C fibres (identified with Bandeiraea simplicifolia isolectin B4) showed low levels of VGLUT2-immunoreactivity, or were not immunoreactive with either VGLUT antibody. As all primary afferents are thought to be glutamatergic, this raises the possibility that unmyelinated afferents, most of which are nociceptors, express a different vesicular glutamate transporter. [source] ELECTROPHYSIOLOGICAL EVIDENCE FOR THE INTERACTION OF SUBSTANCE P AND GLUTAMATE ON A, AND C AFFERENT FIBRE ACTIVITY IN RAT HAIRY SKINCLINICAL AND EXPERIMENTAL PHARMACOLOGY AND PHYSIOLOGY, Issue 12 2006Qi Zhang SUMMARY 1The purpose of the present study was to investigate whether there was a cooperative interaction between substance P (SP) and glutamate (GLU) administered subcutaneously on A, and C primary afferent fibre activity in dorsal hairy skin of the rat in vivo. The single unit activities of A, and C afferent fibres were recorded by isolation of fibre filaments from the dorsal cutaneous nerve branches and the effects of subcutaneous injections of low doses of SP, GLU and SP + GLU on activity were determined. 2Sub-threshold doses of SP (1 µmol/L, 10 µL) administered subcutaneously into the dorsal hairy skin had no effect on the afferent discharges of either A, or C units. 3The afferent discharges of 35% (11/31) of A, fibres and 33% (6/18) of C fibres were increased by local injection of the submaximal doses of GLU (10 µmol/L, 10 µL) into the receptive fields. 4The GLU-induced excitatory response was significantly enhanced by coinjection of subthreshold doses of SP. The mean discharge rates of A, fibres and C fibres were increased from 5.84 ± 1.54 and 5.02 ± 2.65 impulses/min to 19.91 ± 4.35 and 17.58 ± 5.59 impulses/min, respectively, whereas the excitatory proportions of A, and C fibres were increased from 35 and 33% to 84 and 83%, respectively. The duration of the excitation for A, fibres and C fibres was also significantly increased after coinjection of SP + GLU compared with that observed when either substance was given alone. 5The present study provides electrophysiological evidence for an interaction between receptors for SP and GLU on the fine fibres activities in rat hairy skin, which may be involved in the mechanisms of hyperalgesia. [source] | ||||||||||