Marilyn Manson -- Simulates Wrist-Slashing After Paris Jackson Song Dedication

Marilyn Manson took a knife to his arm and simulated a wrist-slashing during his L.A. concert last night ... moments after dedicating a song to Paris Jackson.

The knife is attached to a microphone -- which Manson has used as a prop in previous concerts ... but in the wake of the Paris Jackson song dedication, it had a bigger impact during last night's show.

We broke the story ... hours before Paris took a meat cleaver to her arm at her Calabasas home earlier this week, she "threw a fit" because she wasn't allowed to attend a Marilyn Manson show.

Manson dedicated the song "Disposable Teens" to Jackson last night ... and had previously extended an open offer to Paris to attend his shows whenever she wants.