Neonatal Anti‐NGF Treatment Reduces the Aδ‐ and C‐Fibre Evoked Vasodilator Responses in Rat Skin: Evidence That Nociceptor Afferents Mediate Antidromic Vasodilatation

Abstract

Electrical stimulation of cutaneous nerve Aδ‐fibres can lead to increases in skin blood flow (Jänig and Lisney, J. Physiol. (Lond.), 415, 477–486, 1989). Here we have examined this phenomenon in adult rats treated neonatally with antisera to nerve growth factor between postnatal days 2 and 14. This treatment forces many Aδ nociceptor afferents to take on the phenotype of low‐threshold D‐hair afferents (Lewin et al., J. Neurosci., 12, 1896–1905, 1992). In animals treated this way we found a parallel decrease in the ability of Aδ‐fibres to increase skin blood flow. The increase in blood flow evoked by C‐fibre stimulation was also reduced, but no change was seen in the ability of C‐fibres to elicit neurogenic extravasation in skin. These data may be taken as evidence that in rats, amongst the cutaneous Aδ‐fibres, nociceptor but not D‐hair afferents are capable of producing blood flow changes in the skin.