Disturbance of circadian rhythm in heart rate, blood pressure and locomotive activity at the stroke-onset in malignant stroke-prone spontaneously hypertensive rats

Malignant stroke-prone spontaneously hypertensive rats (M-SHRSP), separated from SHRSP, develop severe hypertension and spontaneously develop stroke a t early ages. Using this model of cerebrovascular stroke, influence of stro ke-onset on the autonomic nervous system was investigated. Heart rate (HR), systolic and diastolic blood pressures (SBP and DBP) and locomotive activi ty were monitored during development of stroke using a telemetry system. St roke-onset was assessed by neurologic symptoms, changes in body weight, flu id intake and serum NOx level. The rat displayed a nocturnal pattern of cir cadian rhythms. At stroke-onset, mean HR over 24 h increased by 20 to 30 bp m and rapidly increased at post stroke, approximately 100 bpm higher than t hat at pre stroke. Circadian variation in HR, which was normally 50 bpm hig her during night than during day, attenuated at stroke-onset, and it was bl unted or reversed at post stroke. BP variation, which was approximately 7 m mHg higher at night than at day, decreased one or two days before stroke-on set and reversed at post stroke, especially in DBP. Insufficient falls in H R and BP during the day mainly accounted for the disturbed circadian variat ions. Variation of locomotive activity also decreased. These changes serve as reliable and accurate markers for stroke-onset in evaluation of drugs fo r the prevention and outcome predictions of stroke.