The notion that intracellular Ca²⁺ (Ca_i²⁺) stores play a significant role in the chemoreception process in chemoreceptor cells of the carotid body (CB) appears in the literature in a recurrent manner. However, the structural identity of the Ca²⁺ stores and their real significance in the function of chemoreceptor cells are unknown. To assess the functional significance of Ca_i²⁺ stores in chemoreceptor cells, we have monitored 1) the release of catecholamines (CA) from the cells using an in vitro preparation of intact rabbit CB and 2) the intracellular Ca²⁺ concentration ([Ca²⁺]_i) using isolated chemoreceptor cells; both parameters were measured in the absence or the presence of agents interfering with the storage of Ca²⁺. We found that threshold [Ca²⁺]_i for high extracellular K⁺ (K_e⁺) to elicit a release response is 250 nM. Caffeine (10-40 mM), ryanodine (0.5 µM), thapsigargin (0.05-1 µM), and cyclopiazonic acid (10 µM) did not alter the basal or the stimulus (hypoxia, high K_e⁺)-induced release of CA. The same agents produced Ca_i²⁺ transients of amplitude below secretory threshold; ryanodine (0.5 µM), thapsigargin (1 µM), and cyclopiazonic acid (10 µM) did not alter the magnitude or time course of the Ca_i²⁺ responses elicited by high K_e⁺. Several potential activators of the phospholipase C system (bethanechol, ATP, and bradykinin), and thereby of inositol 1,4,5-trisphosphate receptors, produced minimal or no changes in [Ca²⁺]_i and did not affect the basal release of CA. It is concluded that, in the rabbit CB chemoreceptor cells, Ca_i²⁺ stores do not play a significant role in the instant-to-instant chemoreception process.