[The role of substance P and catecholamine in the mechanism of pressor response elicited by application of kainic acid to the rostral ventral surface of the medulla oblongata in rat].

Application of kainic acid (KA) to the rostral ventral surface of the medulla oblongata (RVM) produced an increase in mean arterial pressure, accompanied by a decrease in substance P-like immunoreactivity in both spinal cord and medulla oblongata and an elevation of plasma adrenaline (AD) and noradrenaline (NA) content. There were no significant changes in the amounts of AD and NA in other areas of the central nervous system. These responses were effectively abolished by pre-intrathecal injection of D-pro2, D-phe7 or D-Trp8-SP. These results suggest that the pressor responses evoked by activation of RVM might be mediated by a substance P (SP)-containing bulbospinal pathway rather than by a central catecholamine system. SP transmits excitatory information from RVM to the peripheral vasculature via the spinal sympathetic adrenal medulla system, which plays an important role in maintaining vasomotor tone.