Modulatory effects of adenosine on baroreflex activation in the brainstem of normotensive rats

The effects of the adenosine antagonists, 1,3-dipropyl-8-p-sulphenylxanthine (DPSPX) and caffeine, on baroreflex activity were tested in normotensive Sprague-Dawley rats. The microinjection of DPSPX (0.92 nmol) into the nucleus tractus solitarii (NTS) of urethane-anesthetized animals did not modify basal blood pressure or heart rate but inhibited the reflex bradycardia elicited by phenylephrine. Similar inhibitory effects on baroreflex activation were observed after intracisternal administration of caffeine to conscious or anesthetized animals. These results suggest that central endogenous adenosine is involved in the medullary regulation of blood pressure and that adenosine antagonists such as caffeine can inhibit baroreflex activation.