Cerebral aging: implications for the heart autonomic nervous system regulation

The autonomic nervous system (ANS), including sympathetic and parasympathetic neuronal outfl ows, together with the afferent inputs and central control mechanisms, plays a key role in the maintenance of cardiovascular homeostasis. Preganglionic neurons of the sympathetic and parasympathetic systems are localized in the central nervous system, and their axons form synapses on postganglionic effector neurons in peripheral autonomic ganglia. Preganglionic neurons in the ANS utilize acetylcholine as a neurotransmitter, while postganglionic neurons typically employ either noradrenaline (sympathetic) or acetylcholine (parasympathetic). There is now unequivocal evidence that progressive sympathetic activation occurs with aging. This sympathetic stimulation seems to implicate the sympathetic outfl ow to the heart, the skeletal muscle vasculature, and the gut and liver, but to exclude the kidneys. Although the nature of the underlying disturbance in sympathetic control at central level remains largely unknown, the importance of better understanding the central mechanisms implicated in aging-induced sympathetic activation is stressed by the recognition that in a variety of cardiovascular disorders, including heart failure, whose incidence rises with age, the sympathetic nervous system (SNS) is causally involved