Telemetric blood pressure monitoring in conscious rats before and after compression injury of spinal cord

Abnormal cardiovascular control after spinal cord injury (SCI) results in h ypotension soon after injury. Later, paroxysmal hypertension and bradycardi a in response to sensory stimulation below the level of injury develop in m ost people with SCI. In this study, we used a radiotelemetry system, in rat s (n = 7), to investigate the effect of a clinically relevant compression m odel of SCI at T5 spinal segment on mean arterial pressure (MAP) and heart rate (HR) at rest and in response to colorectal distension. The transducers were implanted 1 month before clip compression (50-g) injury and continuou s recording of MAP and HR was established for a period of 2.5 months. SCI w as associated with hypotension (86 +/- 3 nun Hg) at 1 day after injury. In the following 2 days, MAP gradually returned to preinjury levels. By contra st, HR increased at 1 day after SCI and remained unchanged thereafter. Thre e days after SCI, colorectal distension caused an increase in MAP of 8 +/- 2 mm Hg accompanied by bradycardia (-18 bpm). One week after SCI, colorecta l distension induced an increase in MAP of 9 +/- 2 mm Hg and bradycardia (- 41 bpm). In the following days, the magnitude of reflex hypertension gradua lly increased, reaching 21 +/- 4 mm Hg at 1.5 months after SCI. In summary, our data show that resting MAP rapidly returns to control values after SCI . Episodic hypertension associated with autonomic dysreflexia can develop i n rats within 1 month after incomplete SCI.