ABSTRACT
This study evaluated the effect of blockade of the excitatory amino acid (EAA) receptors in the dorsomedial hypothalamic (DMH) area on the ventilatory and cardiovascular responses of the chemoreflex activation in conscious rats. Bilateral microinjection of kynurenic acid (2.7 nmol, n = 6) into the DMH area reduced the tachypneic (+ 264 ± 13 versus + 204 ± 14 cpm, P < 0.05) and pressor (+ 52 ± 5 versus + 31 ± 6 mmHg, P < 0.05) components of chemoreflex but had no effect on the bradycardic component (-214 ± 7 versus -244 ± 17 bpm) of the chemoreflex. The magnitudes of the reduction in pressor and tachypneic chemoreflex responses were not significantly correlated (r = 0.308, P = 0.330). These data indicate that neurons located in the DMH area are activated by chemoreflex; that this activation is mediated via EAA receptors; and that it is essential for the full expression of the respiratory component of the chemoreflex.
