Neurofilament in feline primary afferent neurones: a quantitative immunocytochemical study

Two populations of cat L4 dorsal root ganglion (DRG) neurones were apparent from their Nissl staining with Toluidine blue. One had neurones of all sizes and the other had predominantly small neurones. The size distribution of neuronal profiles in the two populations overlapped and both were approximately normal. They corresponded to the light (L) and small dark (SD) cell populations previously described in rat DRGs. These neurones were examined with four antibodies to neurofilament: RT97, NFH, 155 and anti-68kD. RT97 is specific for the phosphorylated form of the 200 kDa subunit; NFH recognises both phosphorylated and non-phosphorylated forms of this subunit; 155 and anti-68 kDa recognise the 155 kDa and 68 kDa subunits respectively. The clearest differential labelling was seen with NFH and RT97 and this labelling was compared with cell size. High intensity NFH labelling was in a population of neuronal profiles of all sizes and low intensity labelling in a population of predominantly small neuronal profiles. These populations corresponded respectively to the L and SD populations seen with toluidine blue staining. In the rat, these populations can be demonstrated by both NFH and RT97. In contrast in the cat, high intensity RT97 labelling was seen in only 75% of the L neuronal profiles defined with NFH and was also seen in some SD neuronal profiles defined with NFH. It is thus proposed that L and SD cell types are present in the cat DRG and can be demonstrated using the anti-neurofilament marker, NFH.