A, response of the splanchnic and phrenic nerves to peripheral chemoreceptor stimulation with i.v. cyanide (NaCN: 50 μg kg−1) in a urethane-anaesthetized rat, before (left panel) and 5 min after bilateral injection of Kyn (200 mm, 50 nl: right panel) into RVLM. B, effect of Kyn on the cyanide-induced rise in MAP (*P < 0.05; 8 rats). C, effect of Kyn on the cyanide-induced rise in sSND (*P < 0.05; 8 rats).