  We studied magnetoresistance (MR) of nanoconstrictions created in (Ga,Mn)As
epilayers by O+ ion implantation. Original layers exhibit a negative MR that is
plausibly caused by weak localization (WL) effects at the lowest temperatures.
In constricted samples, additionally, jumps of an enhanced conductance appear
on the background of the negative MR, whose positions reflect the hysteresis of
magnetization. We argue that they are manifestation of a suppression of WL due
to the nucleation of a domain wall in the constriction
