Structural and functional changes of cat carotid body following superfusion with Ca2+ and/or Ba2+

The effect of saline solutions containing zero or 2.16 mM of Ca2+ and/or Ba2+ on the cat carotid body superfused in vitro was investigated morphologically and electrophysiologically. The ultrastructure of preparations exposed for 30 min to zero [Ca2+-2.16 mM Ba2+]0 revealed profound reactive alterations among all constituents of the lobule with a loss of granular vesicles from glomus cells. Solutions containing barium ions provoked an initial dramatic increase in nerve discharge which practically disappeared in about 40 min. The zero [Ca2+-2.16 mM Ba2+]0 medium reversed a dopamine-induced inhibitory effect, but did not qualitatively alter the responses to acetylcholine or NaCN during or after the initial increase in activity.