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

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Abstract
The degree of synchronization (DOS) between the afferent spike activity from one stitch of the lateral line of N. maculosus (in vivo) and the mechanical stimulation of 1 neuromast of the same stich 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 .mu.M in Tris-HCl buffer, but was markedly reduced at Ca = 10 .mu.M in MOPS[morpholinopropane sulfonic acid]-KOH buffer. The reduced DOS could be restored by addition of 10-20 mM KCl. Of 4-aminopyridine, 5 mM did not influence the DOS at high Ca concentration, but completely reduced DOS at Ca = 10 .mu.M. D600 (methoxy verapamil) decreased DOS both at high and low Ca concentration.