Carotid Body Chemoreception: Role of Extracellular Ca²⁺

Abstract

In stimulus secretion-coupling, the excitable cells may depolarize first, opening voltagegated calcium channels and allowing Ca²⁺ to enter the cells, activating exocytosis of vesicles and secretion of transmitters, which then act on the target cells. Applying the same model to the carotid body (CB), the role of the [Ca²⁺]o has been investigated in the raising of [Ca²⁺] in the glomus cell (GC) and chemosensory excitation. But the results have been controversial (Buckler & Vaughan-Jones, 1993; Duchen & Biscoe, 1992; Donnelly & Kholwadwala, 1992; Gonzalez et al., 1992; Shirahata & Fitzgerald, 1991). Two different mechanisms have been proposed for the GC [Ca²⁺]_i rise observed during hypoxia: release of Ca²⁺ from mitochondria (Duchen and Biscoe, 1992) and Ca²⁺ entry from the extracellular space through voltage-gated channels (Shirahata & Fitzgerald 1991; Gonzalez et al., 1992).