Neuronal subpopulations in the dorsal root ganglion of the mouse as characterized by combination of ultrastructural and cytochemical features.

The neuronal population of dorsal root ganglia in mouse consists of various classes of ganglion cells which may be divided in turn into subclasses by using several criteria. In class A cells, membrane-bound organelles are distributed ubiquitously throughout the large perikarya. Subclass A alpha (12%), which is characterized by large clumps of Nissl substance separated by narrow strands of neuroplasm, lacks detectable carbonic anhydrase activity. Subclass A beta (16%) displays small clusters of Nissl substance isolated by broad channels of neuroplasm and a moderate activity of carbonic anhydrase. Subclass A gamma (8%) shows the most intense carbonic anhydrase activity and a lack of uptake for [3H]L-glutamine. In class B cells (63%), the small perikarya display a zonal distribution of the organelles. Subclass B alpha contains parallel cisternae of rough endoplasmic reticulum and acid phosphatase isoenzymes present in long and curved Golgi saccules. Subclass B beta displays straight Golgi saccules rich in acid phosphatase isoenzymes and a high affinity uptake for glutamine. Subclass B gamma is characterized by the absence of acid phosphatase isoenzymes and by the presence of substance P-immunoreactivity. Class C cells (1%) have the smallest size and the highest affinity uptake for glutamine. Thus subtypes of primary sensory ganglion cells may be identified by the concomitant use of multiple criteria.