They entered the break on 131-2 in their second innings, having wrested back control of the match by dismissing the visitors for just 141.
Samit Patel is undefeated on 51, made from only 43 deliveries, while Indian Test batsman Chuteshwar Pujara is on 27no on his return to the club, with the pair putting on 69 for the third wicket.
Northants bowler Azharullah, who picked up five wickets on the opening day when Notts were shot out for 213, struck with just the 13th ball of the morning, having opener Jake Libby caught at third slip by Rory Kleinveldt for two. Kleinveldt then picked up the only other wicket to fall, bowling Steven Mullaney for 28.
The visitors’ hopes have been rocked by a couple of injuries. Captain Alex Wakeley has a damaged index finger and wicketkeeper Adam Rossington was struck on the thumb when a skiddy delivery from Azharullah wasn’t taken cleanly.
Both players have left the ground to go to hospital for X-rays.