Influence of Ca2+ on the mechanosensitivity of the hair cells in the lateral line organs of Necturus maculosus.

The degree of synchronization (DOS) between the afferent spike activity from one stitch of the lateral line of Necturus maculosus (in vivo) and the mechanical stimulation of one neuromast of the same stitch was measured under different circumstances. The DOS was found to be independent of changes in the concentration of monovalent cations (Na+, K+ and choline+) in the bulk solution at high Ca concentration (1 mM). DOS was also independent of the Ca concentration in the range 1 mM-1 microM in Tris-HCl buffer, but was markedly reduced at Ca = 10 microM in MOPS-KOH buffer. The reduced DOS, however, could be restored by addition of 10-20 mM KCl. 5 mM of 4-aminopyridine did not influence the DOS at high Ca concentration, but completely reduced DOS at Ca = 10 microM. D600 (a methoxy derivative of verapamil) decreased DOS both at high and low Ca concentration.