BASIC FIBROBLAST GROWTH-FACTOR REGULATES IONIC CURRENTS AND EXCITABILITY OF FETAL-RAT CAROTID-BODY CHEMORECEPTORS

Basic fibroblast growth factor (bFGF) and nerve growth factor (NGF) ar e known mitogens and/or differentiation factors for cells of the sympa thoadrenal lineage. Though carotid body (CB) chemoreceptors (type 1 ce lls) are considered part of this lineage, their response to bFGF is un known and so far they appear unresponsive to NGF in vitro. In this stu dy we use whole-cell recording to investigate whether bFGF (and NGF) c an influence the development of ionic currents in these chemoreceptors , cultured from fetal (E18-19) rat pups. bFGF (10 ng/ml) significantly augmented both transient inward Na+ and outward K+ currents in type 1 cells after only 2 days of treatment; after normalizing for the accom panying increase in cell size, as indicated by whole-cell capacitance, the Na+ current density was nonetheless increased by bFGF. Unlike con trols, bFGF-treated type 1 cells readily fired action potentials follo wing depolarization. These effects were not mimicked by NGF (100 ng/ml ) treatment. Since the carotid body is one of the most richly vascular ized organs and bFGF is a potent angiogenic factor, it is conceivable that variations in local bFGF concentrations during fetal development may contribute to the known species differences in CB chemoreceptor ex citability.