Adrenomedullin (ADM) is a 52-amino-acid peptide originally isolated from a human pheochromocytoma. It is structurally and functionally related to calcitonin gene-related peptide (CGRP) and belongs to the amylin peptide family. Voltage-dependent calcium channels (VDCCs) serve as crucial mediators of membrane excitability and many calcium-dependent functions such as growth of bone, regulation of proliferation, enzyme activity and gene expression. The purpose of this study was to investigate the effects of ADM on VDCCs currents in osteoblasts using a patch-clamp recording method. Murine osteoblastic MC3T3-E1 cells were cultured at 37 C in a 5%(v/v) CO2 atmosphere with alfa-modified minimal essential medium. Fabricated recording pipettes (2-3 M ohm) were filled with the internal solution of the following composition (in mM): 150 CsCl, 5 EGTA, 10 D-glucose, and 10 HEPES. The pH was adjusted to 7.3 with CsOH. Extracellular solution was a solution containing the following (in mM): 115 BaCl2 and 20 HEPES. The pH was adjusted to 7.4 with TEA-OH. Application of 1 micro M ADM rapidly and reversibly facilitated barium current from minus 49 pA to minus 127 pA (159% facilitation). Application of 0.1 micro M ADM rapidly and reversibly facilitated barium current from minus 78 pA to minus 93 pA (19% facilitation).