NADPH-diaphorase expression in neurones and glial cells of the locust brain.

Using NADPH-diaphorase (NADPH-d) staining as a marker for the enzyme nitric oxide synthase (NOS) we investigated the possible sites of nitric oxide (NO) synthesis in the olfactory pathways of an insect brain. Staining of frozen sections revealed NADPH-d activity in neurones and in glial cells. A cluster of intensely stained interneurones innervates the neuropile of the antennal lobe. NADPH-d expression in the mushroom bodies showed a compartmentalized pattern. The mushroom body intrinsic Kenyon cells did not express NADPH-d. The pedunculus and lobes showed fine granular staining and were invaded by NADPH-d-positive mushroom body extrinsic fibres. The expression of NADPH-d in glial cells enclosing the mushroom bodies suggest that insect glial cells may release NO as a messenger molecule.