Electron microscopy and glycosaminoglycan histochemistry of cerebellar stellate neurons.

The stellate neurons of the cerebellar molecular layer have been mostly studied by light and transmission electron microscopy (TEM). However, the freeze-fracture scanning electron microscopy (SEM) and glycosaminoglycan histochemistry of these inhibitory microneurons have not been explored thus far. The freeze-etching technique, the freeze-fracture method for SEM and the conventional techniques for TEM were applied to cerebellar samples of Swiss albino mice and Arius spixii teleost fishes. In addition, Alcian Blue (AB) staining was applied to mouse cerebellar tissue in order to study glycosaminoglycan histochemistry. At the SEM level, the stellate neurons showed a short axonal plexus extending to the nearby secondary and tertiary Purkinje dendritic branches, and 2 to 4 conical dendrites receiving typical axo-dendritic synapses on their shafts. The fractured stellate neurons showed compact nuclear heterochromatin masses and the three dimensional interrelationship of ER and Golgi complex (Novikoff's GERL complex). The surface of the scarce endoplasmic reticulum was observed as strands extending from the nuclear envelope to the inner surface of the plasma membrane. At the TEM level, axosomatic endings of parallel and climbing fibers were distinguished. The cytochemical study revealed a homogeneous alcianophylic cytoplasmic substance, sensitive to hyaluronidase. This was particularly evident around and within the nucleus. The AB results indicated the presence of hyaluronic acid. A complex neuropil formed by Purkinje cell spiny branches, bundles of parallel fibers, spine synapses and Bergmann astrocytic cytoplasm was seen adjacent to the stellate neurons.