Stannous chloride (SnCl2) increases the calcium (Ca) entry into motor nerve terminals through the voltage-dependent Ca channels. The present study has been conducted to determine which type of channel (i.e., L-, N-, or T-type) participates in the Ca entry increased by SnCl2 (0.1 mM)-induced enhancement of the inward Ca current was more strongly inhibited by CdCl2 (50 microM) or omega-conotoxin (0.1 microM) than by NiCl2 (50 microM) or nifedipine (10 microM), respectively. From the results obtained, it is concluded that SnCl2 increases the Ca entry into the nerve terminal by activating the N-type Ca channels.