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

Electrical stimulation of cutaneous nerve Adelta-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 Adelta 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 Adelta-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 Adelta-fibres, nociceptor but not D-hair afferents are capable of producing blood flow changes in the skin.