BOSTON (AP) — An MBTA spokesman says seven people complained of back discomfort after two trolleys made contact in Boston. The trains, one of which was out of service and had no passengers on board, made contact at about 6:40 a.m. Wednesday. The contact occurred near the Cedar Grove Station in Dorchester. No additional information was immediately available. In an unrelated incident, shuttle buses are being used because the Red Line subway between the Harvard and Alewife stations is shut down.