Russell Slade's men sat joint top of the division heading into the weekend's fixtures, but dropped to outright second thanks to Wolves' 3-0 victory at Walsall.
Both sides had chances to take all three points at Meadow Lane, with 11 shots apiece, but neither was able to make the crucial breakthrough.
The point lifts Notts County to within five points of safety.
Nouha Dicko proved the inspiration as Wolves cruised to victory over their near neighbours at the Bescot Stadium, scoring one either side of the break to put the visitors in control.
Bakary Sako made sure of the points and a climb back to the summit with a fine left-footed free-kick on 67 minutes.
Brentford moved to within a point of Orient as two second-half goals handed them a 2-0 victory over Bradford City.
Clayton Donaldson opened the scoring shortly after the hour mark with his 15th goal of the season, before George Saville poked home for the London club's second.
Meanwhile, Preston North End and Peterborough United kept up pressure on the leading duo, picking up a 3-1 win at 10-man Oldham Athletic and a 4-2 home victory over Crewe Alexandra respectively.
At the other end of the table, Stevenage's remarkable revival continued as they climbed to within a point of safety with a 3-1 home victory over Tranmere Rovers.
Jimmy Smith put Stevenage ahead in the 21st minute, before Darius Charles and John Mousinho added their names to the scoresheet after the break, making it four games unbeaten for the hosts.
An own goal from Curtis Obeng - on loan from Swansea City - proved mere consolation for Tranmere, who were dragged further into the relegation dogfight.
Bristol City continued their march towards survival with a 3-2 win against Shrewsbury Town, and Carlisle United suffered a 2-1 defeat at Port Vale.
Elsewhere, Colchester United picked up a first win in seven matches with a 2-1 win against Coventry City, Gillingham scored a late winner to beat Crawley Town 1-0, and MK Dons came from behind to triumph 2-1 at Swindon Town.
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