The effect of topical turpentine on the functional properties of cutaneous afferents in the anaesthetized rat.
Turpentine was applied to the rat dorsal hindpaw over 1.5-3.5 h and afferent activity was recorded for 1.5-7 h after its removal. Increased spontaneous activity from both A- and C-fibres was observed. There was an increase in units with no response to natural stimuli and a reduction in the numbers of all types of afferent unit, with some recovery of the C- and A delta-classes during the recording period. Surviving C-polymodal nociceptor units had normal sensitivity to noxious heat, but higher mechanical thresholds. Thus turpentine application caused no nociceptor sensitization. Instead, the many insensitive units plus the generalized spontaneous firing may be signs of non-specific axonal damage. A general division of irritant chemicals into those that are predominately damaging, like turpentine, and those that generate specific nociceptor firing or sensitization, is proposed.
Leung
K
K
Department of Physiology, University College London, UK.
Lynn
B
B
D000287:Administration, Topical; D000758:Anesthesia; D000818:Animals; D005260:Female; D007509:Irritants / Q000494:pharmacology*; D017078:Laser-Doppler Flowmetry; D009412:Nerve Fibers / Q000187:drug effects / Q000502:physiology; D009475:Neurons, Afferent / Q000187:drug effects* / Q000502:physiology / Q000648:ultrastructure; D009619:Nociceptors / Q000187:drug effects / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D014425:Turpentine / Q000494:pharmacology*
D007509:Irritants; D014425:Turpentine