text: 3. Results 
  
  3.1. Peripheral nerve injury induces a loss of small neurons 
  from the dorsal root ganglion 
  
  Together, our data derived from several different experimental 
  approaches show that a population of small-diameter afferents 
  are lost following peripheral nerve injury. 
  
  3.2. Spared nerve crush or transection results in death of 
  Mrgprd-expressing neurons 
  
  To date, determining cell 
  loss among specific populations of 
  afferent neurons has proved challenging due to the down- 
  regulation of subpopulation-specific marker genes following 
  transection.37,44 To overcome this issue, we took 
  axonal 
  advantage of 
  transgenic strategies to label populations in 
  a manner that persisted after injury. Owing to the bias for the 
  loss of small neurons and the known loss of IB4-binding central 
  terminals postinjury,36 we initially focused on nonpeptidergic 
  nociceptive neurons. We used MrgDChR2-YFP mice to identify 
  neurons belonging to the largest of 
  the 3 classes of non- 
  peptidergic nociceptors, NP1.55,59 To determine whether these 
  neurons are lost following nerve injury, we used a stereological 
  method to quantify L4 DRG MrgD-YFP1 (yellow fluorescent 