Targeting arterial chemoreceptor over-activity in heart failure with a gas

Carotid body: a new target for rescuing neural control of cardiorespiratory balance in disease

Significant insight into the mechanisms involved in chronic heart failure (CHF) have been provided by Schultz and his associates at the University of Nebraska Medical Center with the use of pacing-induced heart failure rabbits. Critical among the CHF mechanisms was the role of the carotid body (CB). The stimulated CB produces a wide array of systemic reflex responses; certainly those in the cardiopulmonary (CP) system are the most important in CHF. This generates a question as to whether the CB could serve as a target for some kind of treatment to reestablish control of cardiorespiratory balance in CHF. Any treatment would have to be based on a solid understanding of the mechanisms of chemosensing by the CB as well as the transducing of that sensing into neural activity sent to the medullary centers and regions of autonomic outflow to the periphery. Two avenues of treatment could be to (1) silence or attenuate the CB's neural output pharmacologically and (2) excise the CBS. There is a long history of CB removal mostly as a remedy for chronic obstructive lung disease. Results have been inconclusive as to the effectiveness of this procedure. But if carefully planned, the procedure might be a helpful treatment.

Oxygen sensing in the carotid body and its relation to heart failure

This brief review first touches on the origins of the earth's oxygen. It then identifies and locates the principal oxygen sensor in vertebrates, the carotid body (CB). The CB is unique in that in human subjects, it is the only sensor of lower than normal levels in the partial pressure of oxygen (hypoxia, HH). Another oxygen sensor, the aortic bodies, are mostly vestigial in higher vertebrates. At least they play a much smaller role than the CB. In such an important role, the many reflexes in response to CB stimulation by HH are presented. After briefly reviewing what CB stimulation does, the next topic is to describe how the CB chemotransduces HH into neural signals to the brain. Several mechanisms are known, but critical steps in the mechanisms of chemosensation and chemotransduction are still under investigation. Finally, a brief glance at the operation of the CB in chronic heart failure patients is presented. Specifically, the role of nitric oxide, NO, is discussed.