Firestone JA, Browning MD. Calcium signalling in bovine adrenal chromaffin cells: additive effects of histamine and nicotine.
Synapse 1994;
17:268-74. [PMID:
7992201 DOI:
10.1002/syn.890170407]
[Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
In a previous report, we described the ability of two secretogogues, histamine and nicotine, to stimulate additive effects on catecholamine (CA) release and synapsin II phosphorylation in bovine adrenal chromaffin cells (BACC) [Firestone and Browning (1992), J. Neurochem., 58:441-447]. We hypothesized that these results were due to the combined effects on cytosolic Ca++ of the two distinct signalling pathways. We therefore examined the intracellular Ca++ signals stimulated by histamine and nicotine, alone and together. In Ca(++)-deficient medium, nicotine-stimulated signals were abolished, whereas histamine-stimulated signals were maintained, demonstrating that nicotine depended entirely on Ca++ influx for its effects. Indeed, the nicotine-stimulated signal could also be prevented using a Ca++ channel blocker, nicardipine. Further, the observation that exposure of BACC to thapsigargin reduced histamine-stimulated Ca++ signals verified that histamine mobilizes Ca++ from intracellular stores. Thus, the two secretogogues mobilize Ca++ from distinct pools. When BACC were stimulated with the two secretogogues together, the resulting Ca++ signal was greater than that from either alone. These data are consistent with a model in which two distinct sources of Ca++ can summate within the cell, producing a greater Ca++ signal and, hence, a greater effect on neurotransmitter release.
Collapse