Increased apomorphine-induced hypothermia precedes development of hypertension in SHRs

Apomorphine produced a greater hypothermic response in spontaneously hypertensive rats (SHRs) than in normotensive Wistar-Kyoto rats (WKYs). Experiments were conducted in SHRs and WKYs of three age groups to determine whether the increased hypothermic responsiveness to apomorphine occurs prior to the development of hypertension. The mean systolic blood pressures (SBPs) of SHRs and WKYs were comparable at 4-6 weeks of age. The mean SBP of SHRs were significantly greater than that of WKYs at both 8-10 and 12-15 weeks of age. Yet SHRs responded to apomorphine with significantly greater hypothermia than WKYs at all three ages. These findings indicate that the hyperresponsiveness of SHRs to apomorphine-induced hypothermia precedes the development of hypertension. This sequence of events is consistent with the hypothesis that central DA systems play a role in development of hypertension in SHRs.