Geometric considerations of nitric oxide cyclic GMP signalling in the glomerular neuropil of the locust antennal lobe

Using NADPH-diaphorase staining as a marker for nitric oxide (NO) synthase and an antiserum against cyclic GMP, we recently reported the anatomical distribution of NO donor and target cells in the antennal lobe, the principal olfactory neuropil of the locust. The most striking NADPH-diaphorase activity in the olfactory pathway is concentrated in a cluster of intensely stained local interneurones innervating the glomeruli. After incubation of tissue in a NO donor and inhibition of phosphodiesterase activity, neurones of this cluster expressed cyclic GMP-immunoreactivity in the cell body and neurites. Here we examine the importance of the arrangement of NO donor and target cells for information processing in the glomeruli. The cellular organization of the NO-cyclic GMP system in olfactory interneurones, and the dendritic branching pattern, suggest that NO may not only act as intercellular, but also as intracellular messenger molecule in the glomerular neuropil of the antennal lobe.