EVIDENCE FOR THE INVOLVEMENT OF ENDOGENOUS ASPARTATE IN THE MEDIATIONOF CAROTID CHEMORECEPTOR REFLEXES IN THE ROSTRAL VENTROLATERAL MEDULLA OF THE RAT

2-Amino-5-phosphonovalerate (AP5; 153 pmol) injected into the rostral ventrolateral medulla (RVLM) inhibited presser responses induced by ca rotid chemoreceptor stimulation. AP5 also inhibited presser responses to aspartate (0.75 nmol) but not to glutamate (0.53 nmol) similarly in jected. High K+ (50 mM) released endogenous aspartate and glutamate in a Ca2+-dependent manner from the RVLM. Chemoreceptor stimulation caus ed a release of aspartate but not of glutamate in the RVLM, and sinus nerve denervation abolished the release of aspartate. Increases in blo od pressure induced by intravenous phenylephrine did not release aspar tate. These results support the hypothesis that endogenous aspartate i n the rat RVLM is involved in the mediation of chemoreceptor reflexes. (C) 1997 Elsevier Science Ireland Ltd.