Voltage-dependent potassium channels contribute to the electrical properties of nerve and muscle by affecting action potential shape and duration. The complexity of the currents generated is further enhanced by the presence of accessory beta subunits. Here we report that while all Kvbeta mRNA isoforms are present in rat brain, muscle tissues express only Kvbeta1 (Kvbeta1.1-Kvbeta1.3) and Kvbeta2, but not Kvbeta3. Kvbeta subunits were close regulated through post-natal development in brain and striated muscle, as well as during myogenesis in the rat skeletal muscle cell line L6E9. While the alternatively spliced Kvbeta mRNA products from Kvbeta1 gene were differentially expressed, Kvbeta2.1 was associated with myogenesis. These results show that Kvbeta genes are strongly regulated in muscle and suggest a physiological role for voltage-gated K(+) channels during development and myotube formation.