 After the completion of the berlin wall , the U8 was severely impaired.In the north, only the stations Voltastraße and Gesundbrunnen could be used by West Berliners .A tiny line of 2 stations that was little used by the Berliners - a condition that lasted until October 5, 1977 as the U8 was extended to Osloer Straße to interchange to the U9.