Molecular mechanisms of sleepwake regulation: roles of prostaglandins D1 and E2

An automatic record playing apparatus comprises a rotating member adapted to rotate together with a tone arm and having a projection thereon, a rotation driving member rotated forward and backward over a predetermined range during a predetermined operational period by a rotating force of a turntable, and a pushing means provided on the rotation driving member and adapted to push the projection to rotate the rotating member for returning the tone arm unitarily therewith toward outside of a record disc as the rotation driving member effects initial forward rotation. The pushing means having a first portion for pushing the projection in one rotational direction of the rotating member, and a second portion for pushing elastically the projection in the direction other than the rotational direction of the rotating member. The rotating member being rotated in the result, that the projection is pushed by the first portion of the pushing means in a state where unnecessary revolution thereof is obstructed by the second portion.