Receptive properties of afferent nerve fibres associated with the rat saphenous vein.

We tested afferent fibres isolated from the saphenous nerve for their responses to mechanical, osmotic and chemical stimuli applied to a vascularly isolated segment of the saphenous vein in the rat. Fifteen units were excited by local mechanical stimulation and many of them were also activated by distension of the venous segment, however exclusively by presumably noxious pressures. Most mechanosensitive fibres were excited by one of the three pain-producing substances, hyperosmotic saline (HS), potassium chloride (KCl) and bradykinin. Three fibres which were insensitive to mechanical stimulation, responded to injection of HS or KCl into the venous segment. We conclude that the venous afferents most likely have nociceptive function. Most are considered to be polymodal.