Stimulatory actions of pituitary adenylate cyclase-activating polypeptide (PACAP) in rat carotid glomus cells.

The carotid bodies are the major peripheral chemoreceptors that detect changes in arterial blood oxygen level. PACAP-deficient mice are prone to sudden neonatal death and have reduced respiratory response to hypoxia and hypercapnia. To investigate whether PACAP contributes to the chemotransduction in carotid body, we studied the action of PACAP on glomus cells isolated from rat carotid body. We found that PACAP triggered cytosolic [Ca2+] ([Ca2+]i) rise in glomus cells. Removal of extracellular Ca2+ reversibly inhibited the PACAP-mediated [Ca2+]i rise. Under voltage clamp conditions and in the presence of tetraethylammonium (TEA) and Cd2+, PACAP reduced the outward current evoked at positive potentials. We suggest that the inhibition of a TEA-insensitive current is a mechanism underlying the PACAP-mediated [Ca2+]i rise in glomus cells. The loss of the stimulatory action of PACAP in glomus cells may partly account for the reduction in chemoresponse in the PACAP-deficient mice.