title: Sensory and sympathetic nerve contributions to the cutaneous vasodilator response from a noxious heat stimulus.
abstract: We investigated the roles of sensory and noradrenergic sympathetic nerves on the cutaneous vasodilator response to a localized noxious heating stimulus. In two separate studies, four forearm skin sites were instrumented with microdialysis fibres, local heaters and laser-Doppler probes. Skin sites were locally heated from 33 to 42 °C or rapidly to 44 °C (noxious). In the first study, we tested sensory nerve involvement using EMLA cream. Treatments were as follows: (1) control 42 °C; (2) EMLA 42 °C; (3) control 44°C; and (4) EMLA 44 °C. At the EMLA-treated sites, the axon reflex was reduced compared with the control sites during heating to 42 °C (P < 0.05). There were no differences during the plateau phase (P > 0.05). At both the sites heated to 44 °C, the initial peak and nadir became indistinguishable, and the EMLA-treated sites were lower compared with the control sites during the plateau phase (P < 0.05). In the second study, we tested the involvement of noradrenergic sympathetic nerves in response to the noxious heating using bretylium tosylate (BT). Treatments were as follows: (1) control 42 °C; (2) BT 42 °C; (3) control 44 °C; and (4) BT 44 °C. Treatment with BT at the 42 °C sites resulted in a marked reduction in both the axon reflex and the secondary plateau (P < 0.05). At the 44 °C sites, there was no apparent initial peak or nadir, but the plateau phase was reduced at the BT-treated sites (P < 0.05). These data suggest that both sympathetic nerves and sensory nerves are involved during the vasodilator response to a noxious heat stimulus.
authors: Department of Kinesiology, The University of Alabama, Tuscaloosa, AL 35401, USA.
authors: Stephen J
authors: SJ
authors: Carter
authors: Gary J
authors: GJ
authors: Hodges
mesh_terms: D000328:Adult; D000779:Anesthetics, Local; D001950:Bretylium Tosylate / Q000494:pharmacology; D005260:Female; D006358:Hot Temperature; D006801:Humans; D008012:Lidocaine; D000077442:Lidocaine, Prilocaine Drug Combination; D008297:Male; D011318:Prilocaine; D012039:Regional Blood Flow / Q000502:physiology; D012867:Skin / Q000098:blood supply* / Q000294:innervation; D012881:Skin Temperature; D013564:Sympathetic Nervous System / Q000187:drug effects / Q000502:physiology*; D014664:Vasodilation / Q000502:physiology*; D014665:Vasodilator Agents / Q000494:pharmacology
chemical_list: D000779:Anesthetics, Local; D000077442:Lidocaine, Prilocaine Drug Combination; D014665:Vasodilator Agents; D011318:Prilocaine; D001950:Bretylium Tosylate; D008012:Lidocaine