Lee Hughes' 82nd-minute penalty, scored just after Craig Westcarr had missed a spot-kick, looked to have earned the Magpies a valuable three points in their battle against relegation. But German-born striker Schlupp netted in the fifth minute of added time to share the points.
Karl Hawley saw two shots blocked and one go wide in a high-tempo opening five minutes, before Lewis Grabban's half-volley forced Stuart Nelson to save with his legs.
Mike Edwards got a tame header on target before Schlupp's powerful shot stung Nelson's palms and Robbie Simpson headed wide.
In the 78th minute, a shot was blocked by Karleigh Osborne's hand, but Simon Moore dived to his right to keep Westcarr's penalty out. Four minutes later, Simpson was the handball offender and Hughes made no mistake.
Notts looked like they had held out, but Schlupp picked up on Sam Saunders' pass and fired past Nelson with virtually the last kick of the game.
Source: PA
Source: PA