The cardiovascular responses to chemoreflex activation are not changed by isolated blockade of NMDA or non‐NMDA receptors in the dorsomedial hypothalamus

Abstract

Studies from our laboratory have shown that microinjection of kynurenic acid, a non‐selective antagonist at NMDA and non‐NMDA receptors, into the dorsomedial hypothalamus (DMH) reduced the pressor response and abolished the behavioral response of chemoreflex. This study evaluated the effect of selective blockade of NMDA or non‐NMDA receptors on the cardiovascular responses of the chemoreflex. Bilateral microinjection of AP‐5 into the DMH produced no significant changes on the pressor response (+47 ± 2 mmHg vs 44 ± 3 mmHg) and bradycardia (−245 ± 24 vs −244 ± 27 bpm) of the chemoreflex; however, it was able to reduce the cardiovascular responses induced by NMDA (+21 ± 1 vs 8 ± 2 mmHg; +135 ± 13 vs 69 ± 18 bpm). Bilateral microinjection of CNQX into the DMH also produced no changes on the pressor response (+44 ± 9 vs +36 ± 8 mmHg) and bradycardia (−228 ± 34 vs −219 ± 32 bpm) of the chemoreflex, but significantly reduced the cardiovascular responses induced by AMPA (+21 ± 2 vs +5 ± 2 mmHg; +111 ± 5 vs +40 ± 17 bpm). These results indicate that isolated blockade of NMDA receptors or non‐NMDA receptors of the DMH does not promote changes in cardiovascular responses to chemoreflex. Support: CNPq/FAPEMIG.