Adenosine and glutamate modulate the cardiovascular responses of angiotensins II and III in the area postrema of rats.

The purpose of this study was to determine the interactions of the renin-angiotensin system with adenosine and glutamate in the area postrema (AP) of rats. Male Sprague-Dawley rats were anesthetized with urethane. Adenosine, angiotensins (Ang) II, III and their antagonist 1,3-Dipropyl-8-p-sulfophenylxanthine (DPSPX), [Sar1Ile7]Ang III and glutamate antagonist, L-glutamic acid diethyl ester (GDEE) were microinjected into the AP of rats. Our results demonstrated that microinjection of DPSPX significantly attenuated the depressor and bradycardic effects of Ang II and III at low (9.6 pmol) and high dose (480 pmol) of Ang II in normotensive rats. To test the interaction of glutamate and renin-angiotensin system, we found that glutamate antagonist, GDEE, markedly lowered depressor and bradycardic responses of Ang II but did not influence Ang III in rats. On the other hand, microinjection of the Ang antagonist [Sar1Ile7]Ang III 10 min prior to the injection of adenosine significantly altered the cardiovascular effects of adenosine in the AP. In conclusion, the endogenous adenosine and glutamate may influence the renin-angiotensin system on cardiovascular responses in the AP of rats.