[Age-related blood pressure reaction in spontaneously hypertensive rats in passive orthostasis].

Blood pressure responses to tilting were studied in spontaneously hypertensive rats (SHR) and Wistar-Kyoto rats (WKY) at different ages. The increase in blood pressure due to tilting was significantly higher in SHR with a developed hypertension (26 week-old) than in WKY rats of the same age, whereas the increase was not significantly different in SHR with a still developing hypertension (10 week-old), compared to WKY rats. Yet, even in 10 week-old SHR, there was a significantly higher increase after treatment with naloxone (0.4 mg/kg) then in WKY rats. Obviously, there are differences in the endogenous opiates between the 10 week-old SHR and WKY rats.