Cardiovascular responses to NMDA injected into nuclei of hypothalamus or amygdala in conscious rats

The nuclei of hypothalamus and amygdala have been shown to be involved in t he central cardiovascular homeostasis. Recent studies suggest that glutamat e-containing neurons have an important role in the regulation of the centra l cardiovascular function. In this study, we demonstrate the roles of the c entral nucleus of the amygdala and the paraventricular nucleus of the amygd ala and the paraventricular nucleus or the dorsomedial nucleus of the hypot halamus in N-methyl-D-aspartate (NMDA) induced blood pressure and heart rat e changes in conscious Sprague-Dawley rats. Intracerebroventricular or pare nchymal injections of NMDA evoke increases in arterial pressure. The NMDA-i nduced elevations in brood pressure are more prominent when NMDA is adminis tered into the dorsomedial nucleus of the hypothalamus, Microinjections of NMDA into the dorsomedial hypothalamus exert significant heart rate increas es, whereas NMDA when administered into the paraventricular nucleus of the hypothalamus or into the central nucleus of the amygdala has no significant effect on the heart rate. The dorsomedial nucleus of the hypothalamus is f ound to be the most effective site in this respect, The present study provi des strong evidence for the tonic glutamatergic influence on blood pressure and heart rate via NMDA receptors located within the dorsomedial nucleus a nd to a lesser extent via those located within the paraventricular nucleus of the hypothalamus. Copyright(C) 2000 S. Karger AG, Basel.