Spatial periodicity of NADPH-diaphorase and synaptophysin, but not SNAP-25, reactivity in the monkey cerebellar cortex.

We recently described a parasagittal patchy organisation of nicotinamide adenine dinucleotide phosphate diaphorase (NADPH-d) activity in the granular layer of the rat cerebellum. We now report the pattern of NADPH-d distribution in the primate cerebellum and its relationship to two synaptic proteins, synaptophysin and synaptosomal associated protein 25 kDa (SNAP-25), using histochemistry and immunocytochemistry. NADPH-d reactivity was localised in the molecular and granular layers (ML, GL) and a subset of infraganglionic plexuses (IGPs), but not in the Purkinje cell layer and the white matter. In ML, the histochemical reactivity was dense and relatively homogeneous in the neuropil, and moderate in the stellate cells. A patchy organisation of NADPH-d in GL was detected in both horizontal and parasagittal sections. In the IGPs staining for NADPH-d revealed modular positive zones alternating with negative ones. The positive and negative IGP zones were usually congruent with the high and low NADPH-d reactivity in GL, respectively. Both synaptic proteins were strongly expressed in the neuropil in ML and GL, and their patterns were relatively homogeneous. However, synaptophysin was present in a subpopulation of IGPs organised in modules which corresponded to those expressing NADPH-d. Our results indicate that the NADPH-d modular system is more complicated in the primate cerebellum than in the rat. In addition, we have provided suggestive evidence of a co-expression of NADPH-d and synaptophysin in selected IGP modules in primate cerebellum, which suggests that nitric oxide may be involved in the activity of the Purkinje cells by affecting the basket cell synaptic input.