Tetrodotoxin-sensitive action potentials in smooth muscle of mouse vas deferens.

Action potentials were recorded during impalements of some but not all smooth muscle cells of mouse vas deferens in response to both nerve stimulation and intracellular current injection. They were resistant to blockade by nifedipine (0.1-1.0 microM) but were blocked by tetrodotoxin (TTX, 0.2-1.0 microM) when this was added in the presence of nifedipine. It is suggested that voltage-dependent sodium (Na+) channels are present in mouse vas deferens that function to amplify calcium (Ca2+) influx through voltage-dependent Ca2+ channels.