Kenny Jackett claimed all three points at Meadow Lane thanks to Ethan Ebanks-Landell's first senior goal, the 20-year-old defender lashing home a left-foot shot in the 76th minute after the Magpies' defence had failed to clear James Henry's free-kick.
County remain rooted to the foot of the table after suffering a third successive defeat under new boss Shaun Derry who was taking charge of a league game for the first time.
Leyton Orient's long reign at the summit was ended after they suffered their first home defeat of the season as they went down 1-0 to Preston.
North End extended their unbeaten league run to five matches and consolidated their place in the play-off positions courtesy of Joe Garner's ferocious 33rd-minute volley from Keith Keane's cross.
Peterborough, who do not play until Monday, remain in third place but they are now only two points clear of Preston and Brentford.
The Bees notched their fifth successive league win by demolishing Crewe 5-0 at Griffin Park.
Marcello Trotta, Adam Forshaw and George Saville were all on target for Brentford before Clayton Donaldson struck twice in 10 minutes against his former club.
Swindon and Rotherham are up to sixth and seventh respectively after claiming valuable away wins.
The Robins prevailed 2-1 at Colchester with Nicky Ajose and Dany N'Guessan scoring from close range either side of half-time before Magnus Okuonghae pulled a goal back for the U's.
The Millers brushed aside Stevenage 3-0 at the Lamex Stadium with Ben Pringle, Claude Davis and Michael O'Connor all on target.
Sheffield United remain firmly in the drop zone after losing 2-1 to Gillingham at Bramall Lane.
Danny Kedwell put the Gills ahead after seven minutes and substitute Cody McDonald sealed the win in the 47th minute after Chris Porter (19) had replied for the Blades.
A late strike by substitute Billy Clarke snatched a point for Crawley in a 1-1 draw against Carlisle and ended a run of four straight league defeats without a goal.
Liam Noble had fired Carlisle ahead two minutes after half-time from the penalty spot, but Crawley's comeback extended the Cumbrians' poor record of just one win in their last nine games.