Neuromodulation of Cardiac Ischemic Pain: Role of the Autonomic Nervous System and Vasopressin.

ABSTRACT

Cardiac pain is an index of cardiac ischemia that helps the detection of cardiac hypoxia and adjustment of activity in the sufferer. Drivers and thresholds of cardiac pain markedly differ in different subjects and can oscillate in the same individual, showing a distinct circadian rhythmicity and clinical picture. In patients with syndrome X or silent ischemia, cardiac pain intensity may cause neurogenic stress that potentiates the cardiac work and intensifies the cardiac hypoxia and discomfort of the patient. The reasons for individual differences in cardiac pain sensation are not fully understood. Thus far, most attention has been focused on inappropriate regulation of the heart by the autonomic nervous system, autacoids, and cardiovascular hormones. Herein, we summarize evidence showing that the autonomic nervous system regulates cardiac pain sensation in cooperation with vasopressin (AVP). AVP is an essential analgesic compound and it exerts its antinociceptive function through actions in the brain (the periaqueductal gray, caudate nucleus, nucleus raphe magnus), spinal cord, and heart and coronary vessels. Vasopressin acts directly by means of V1 and V2 receptors as well as through multiple interactions with the autonomic nervous system and cardiovascular hormones, in particular, angiotensin II and endothelin. The pain regulatory effects of the autonomic nervous system and vasopressin are significantly impaired in cardiovascular diseases.