[Effect of naloxone on the blood pressure response to tilting on spontaneously hypertensive rats].

The influence of naloxone on the blood pressure response to tilting was studied in spontaneously hypertensive rats (SHR) and Wistar-Kyoto rats (WKY). At the age of 5 weeks there were no significant differences in baseline blood pressure or the blood pressure response to tilting between both strains. After pretreatment with naloxone (0.4 mg/kg) there was a significantly higher increase of blood pressure due to tilting in SHR than in WKY rats. At the age of 26 weeks when in SHR the hypertension was fully developed the blood pressure response to tilting was significantly different from that in WKY rats and pretreatment with naloxone had no longer any influence. These results suggest a possible role of endogenous opiates in the development of hypertension.