Regan has not started a game for Rovers since the 6-1 defeat at Walsall last month and the arrival of right-back Danny Senda has seen the 30-year-old fall further down the pecking order at the Memorial Stadium.
Regan has twice played under current Notts boss Paul Ince - at Macclesfield and MK Dons.
He will go straight into the Notts squad for the home game against Charlton on Friday night.
Meanwhile, David Martin has extended his stay at the Memorial Stadium from Derby until April 23.
Source: PA
Source: PA