The rat as a model of chronic recurrent episodic hypoxia and effect upon systemic blood pressure.

The systemic arterial blood pressure response to obstructive sleep apnea (OSA) in humans is usually repetitive (with each apnea) acute elevation with return to near baseline following the apnea. In addition, it is believed by most investigators that chronic diurnal elevation of systemic blood pressure may result from repetitive nightly apneas in humans, resulting in systemic hypertension in about 50-70% of sleep apnea patients. Mechanisms of the chronic elevation in blood pressure are difficult to investigate in humans because it may take many years of repetitive apneas for sustained daytime blood pressure to develop. The rat is an especially good animal to use to investigate these mechanisms because of its use as a model in many types of hypertension. The authors have examined the response to chronic episodic hypoxia (for 35 consecutive days) in several strains of rats, discovering that systemic blood pressure (BP) remains chronically elevated in the absence of hypoxic stimulation after this period. This manuscript reviews the findings in this model after various interventions in the neurochemical and neuroendocrine mechanisms controlling BP in this animal.