Baroreflex function and centrally acting antihypertensive drugs
The baroreflex is a neural circuit that has powerful effects on blood pressure and heart rate. First recognized in the 1920s (Koch and Mies 1929), it is now known to involve sensory endings (arterial baroreceptors) in both the carotid sinus and the aortic arch. These produce afferent impulses which are transmitted via the glossopharyngeal (carotid) and vagus (aortic) nerves to synapses within the nucleus tractus solitarius of the medulla. Ultimately, blood pressure and heart rate are affected by parallel sympathetic and parasympathetic modulation. Following the initial description of the baroreflex, it was speculated that a primary disturbance of its function might lead to hypertension in man. This speculation remains active today, supported by observations that impairment of the baroreflex function can produce hypertension in animals and in man. The development of centrally acting antihypertensive drugs, including clonidine hydrochloride, has provided further information about the neurophysiology of the baroreflex, including evidence that baroreflex modulation may be a component action of such drugs.
KeywordsPlacebo Depression Neuropathy Hydrochloride Noradrenaline
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