EXCITATORY AMINO-ACID RECEPTORS IN THE PARAVENTRICULAR HYPOTHALAMIC NUCLEUS MEDIATE PRESSOR-RESPONSE INDUCED BY CAROTID-BODY CHEMORECEPTOR STIMULATION IN RATS

In urethane-anesthetized rats with spinal transection, antagonists of excitatory amino acid receptors; P2 purinoceptors and adrenoceptors we re microinjected into the paraventricular hypothalamic nucleus (PVN) a nd their effects on the presser response evoked by carotid body chemor eceptor stimulation were examined. Microinjections of the nonselective excitatory amino acid antagonist kynurenate, the non-NMDA receptor an tagonist CNQX and the NMDA antagonist 2-amino-5-phosphonovalerate (AP5 ) into the PVN inhibited the chemoreceptor reflex-induced presser resp onse. The excitatory amino acid agonist L-glutamate injected into the PVN produced an increase in blood pressure. The P2 purinoceptor antago nist suramin did not affect the presser response and ATP did not affec t basal blood pressure. The alpha adrenoceptor antagonist phentolamine , prazosin and yohimbine also inhibited the chemoreceptor-induced pres ser response, while the beta antagonist propranolol did not affect it. These findings indicate that excitatory amino acid receptors and alph a adrenoceptors in the PVN are involved in mediating the presser respo nse induced by carotid body chemoreceptor stimulation in rats.