Autonomic innervation of the carotid body: role in efferent inhibition.
The carotid body (CB) is a chemosensory organ that monitors blood chemicals and initiates compensatory reflex adjustments to maintain homeostasis. The 'afferent' sensory discharge induced by changes in blood chemicals, e.g. low PO(2) (hypoxia), is relayed by carotid sinus nerve (CSN) fibers and has been well studied. Much less is known, however, about a parallel autonomic (parasympathetic) 'efferent' pathway that is the source of CB inhibition. This pathway is the focus of this review which begins with a historical account of the early findings and links them to more recent data on the source of this innervation, and the role of endogenous neurotransmitters in efferent inhibition. We review evidence that these autonomic neurons are embedded in 'paraganglia' within the glossopharyngeal (GPN) and CSN nerves, and for the role of nitric oxide (NO) in mediating efferent inhibition. Finally, we discuss recent data linking the action of hypoxia and a key CB neurotransmitter, i.e. ATP, to potential mechanisms for activating this efferent pathway.
Campanucci
Verónica A
VA
Department of Biology, McMaster University, Hamilton, Ontario, Canada.
Nurse
Colin A
CA
D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D017776:Autonomic Pathways; D002344:Carotid Body / Q000033:anatomy & histology* / Q000502:physiology*; D004525:Efferent Pathways; D005930:Glossopharyngeal Nerve / Q000033:anatomy & histology; D006801:Humans; D000860:Hypoxia / Q000378:metabolism / Q000503:physiopathology; D008959:Models, Neurological; D009569:Nitric Oxide / Q000378:metabolism
D009569:Nitric Oxide; D000255:Adenosine Triphosphate