Effect of Ischaemia and Reperfusion on discharge patterns of nociceptive afferent nerve fibres in the rat tail
Date
1996-03
Authors
Mas, Ilario Dal
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Abstract
In rats anaesthetised with enflurane, Iexamined.the response of coccygeal primary
afferents fibres to noxious thermal and mechanical stimulation and to innocuous
brushing, during transient ischaemia and reperfusion of their receptive fields on
the tail. Ischaemia was induced by occluding the blood supply to the tail for 30
min using a tourniquet. I discovered four different groups of afferent fibres,
distinguished by conduction velocity and modality, A{3fibres responding to both
brush and pinch of their receptive fields showed decreased sensitivity to brush
during both ischaemia and reperfusion; Ao fibres responding to pinch were
unaffected by either ischaemia or reperfusion, C fibres responding to noxious heat
(49ยท C) and pinch showed hypersensitivity during reperfusion, especially
immediately after release of the tourniquet. Another group of C fibres,
presumably chemosensitive, became more actiVA during ischaemia and exhibited
a 7-fold increase in firing rate during receptive field reperfuslon in the absence
of obvious stimuli.
These results indicate that during reperfuslon of the rat tail following transient
ischaemia, myelinated fibres do not increase their input to the CNS, while C
fibres became more active and showed sensitization to noxious stimulation of their
receptive fields. The enhanced CNS nociceptive activity which occurs during
reperfusion consequently results from both peripheral and. central sensitization.