Browsing by Author "Bostock, Hugh"
Now showing 1 - 3 of 3
Results Per Page
Sort Options
Item A search for activation of C-nociceptors by sympathetic fibers in complex regional pain syndrome(2010) Campero, Mario; Bostock, Hugh; Baumann, Thomas; Ochoa, JoséObjective—Although the term ‘reflex sympathetic dystrophy’ has been replaced by ‘complex regional pain syndrome’ (CRPS) type I, there remains a widespread presumption that the sympathetic nervous system is actively involved in mediating chronic neuropathic pain [“sympathetically maintained pain” (SMP)], even in the absence of detectable neuropathophysiology. Methods—We have used microneurography to evaluate possible electrophysiological interactions in 24 patients diagnosed with CRPS I (n=13), or CRPS II (n=11) by simultaneously recording from single identified sympathetic efferent fibers and C nociceptors, while provoking sympathetic neural discharges in cutaneous nerves. Results—We assessed potential effects of sympathetic activity upon 35 polymodal nociceptors and 19 mechano-insensitive nociceptors, recorded in CRPS I (26 nociceptors) and CRPS II patients (28 nociceptors). No evidence of activation of nociceptors related to sympathetic discharge was found, although nociceptors in 6 CRPS II patients exhibited unrelated spontaneous pathological nerve impulse activity. Conclusion—We conclude that activation of nociceptors by sympathetic efferent discharges is not a cardinal pathogenic event in either CRPS I or CRPS II patients. Significance—This study shows that sympathetic-nociceptor interactions, if they exist in patients communicating chronic neuropathic pain, must be the exceptionItem Activity-dependent slowing properties of an unmyelinated low thresh old mechanoreceptor inhuman hairy skin(2011) Campero, Mario; Bostock, Hugh; Baumann, Thomas K.; Ochoa, Jose L.It has been previously shown that unmyelinated afferent fibres in human skin are differentiated not only by their receptor characteristics, but also by their profiles of activity-dependent slowing. One type of profile, described originally as 'type 3', is different from that of nociceptors (type 1), cold afferents (type 2) and sympathetic efferents (type 4), in that these fibres display a minimal activity-dependent slowing (similar to 1% at 2 Hz). However, their function remains to be determined. Here we describe one unit with a typical 'type 3' activity-dependent slowing profile recorded from an undamaged fascicle of the superficial peroneal nerve of a patient. Its conduction velocity was 1.8 ms(-1) and it slowed by 1.3% during the 2 Hz tetanus. This unit had a mechanical receptive field in the hairy skin and responded readily to weak mechanical stimuli, and not to cold. This suggests that the low threshold unmyelinated mechanoreceptors recently described in human hairy skin are probably endowed with a 'type 3' activity-dependent profile. (C) 2011 Elsevier Ireland Ltd. All rights reserved.Item Unmyelinated afferents in human skin and their responsiveness to low temperature(2010) Campero, Mario; Bostock, HughIn humans, there are different types of cutaneous cold-sensitive afferents responsible for cold sensation and cold pain. Innocuous cold is primarily mediated by a population of slow A delta afferents, based on psychophysical and neurophysiological studies. Noxious cold (usually below 15 ◦C) is mediated, at least in part, by polymodal nociceptors. There is also a population of unmyelinated afferents responsive to innocuous low temperature, some of which also respond to heat, whose sensory function has not been completely defined. A paradoxical hot/burning evoked by cooling is unmasked by A-fibre block, and similar sensations are evoked by applying simultaneous cool and warm stimuli to adjacent skin areas. These unmyelinated fibres activated by innocuous cooling (and heating) may contribute to this hot/burning sensation, along with other thermoregulatory functions.