Effect of neonatal treatment with capsaicin on the numbers and properties of cutaneous afferent units from the hairy skin of the rat.
Neonatal treatment with capsaicin caused a 40% reduction in the number of C-fibres in the rat saphenous nerve. Within the reduced total the proportion of nociceptive C fibres was similar in both capsaicin-treated and untreated rats. No change was found in the conduction velocities or firing thresholds (to pressure and to heat) in A-fibre and C-fibre nociceptors. The perimeters of axons were also unchanged by capsaicin. From a comparison of the morphometric and conduction velocity (v) data it is suggested that in the rat saphenous nerve v (m/s) = 1.9 X axon perimeter (micron) for A fibres and v = 0.44 X square root of the axon perimeter for C fibres.
D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D000831:Animals, Newborn; D002211:Capsaicin / Q000494:pharmacology*; D008465:Mechanoreceptors / Q000187:drug effects; D008854:Microscopy, Electron; D009431:Neural Conduction / Q000187:drug effects; D009475:Neurons, Afferent / Q000187:drug effects; D009619:Nociceptors / Q000187:drug effects; D051381:Rats; D012867:Skin / Q000294:innervation*; D013127:Spinal Nerves / Q000187:drug effects* / Q000648:ultrastructure
D002211:Capsaicin