Parvalbumin antibody - Anyone have suggestions?

I’m trying to stain for Parvalbumin in DRG neurons. I’ve been using the Swant Rabbit PV27 antibody, which seems to be the most widely used PV ab for this purpose. I’m using at 1:1000 concentration. Pretty standard IHC conditions: 4% PFA, 1 hour post fix, 20 um cryostat sections. BSA blocking/ab buffers, with 0.2% triton.

Some sections are decent, with clear PV neurons. Others are just a diffuse signal with the positive neurons not standing out. This is even on the same slide! It’s weird. Also, there is always an edge effect, where there is nonspecific signal at the boundary of the DRG slice. I’ve seen this many times now, and I know my slices are not drying out. My labmates have used the ab and have had the same problem.

So are there any specific tricks for PV? Less fixation? Different antibody? Any tips would be greatly appreciated.