NITRIC-OXIDE SYNTHESIS IN LOCUST OLFACTORY INTERNEURONS

The brain of the locust Schistocerca gregaria contains a nitric oxide synthase (NOS) that has similar properties to mammalian neuronal NOS, It catalyses the production of equimolar quantities of nitric oxide (N O) and citrulline from L-arginine in a Ca2+/calmodulin- and NADPH-depe ndent manner and is inhibited by the N-omega-nitro and N-omega-monomet hyl analogues of L-arginine. In Western blots, an antiserum to the 160 kDa rat cerebellar NOS subunit recognises a locust brain protein with a molecular mass of approximately 135 kDa, NOS is located in several parts of the locust brain, including the mushroom bodies, but it is pa rticularly abundant in the olfactory processing centres, the antennal lobes, Here it is present in two groups of local interneurones (a pair and a cluster of about 50) that project into the neuropile of the ant ennal lobes, The processes of these neurones terminate in numerous glo merulus-like structures where the synapses between primary olfactory r eceptor neurones and central interneurones are formed, NOS-containing local interneurones have also been identified in the mammalian olfacto ry bulb, suggesting that NO performs analogous functions in locust and mammalian olfactory systems, As yet, nothing is known about the role of NO in olfaction, but it seems likely that it is involved in the pro cessing of chemosensory input to the brain, The locust antennal lobe m ay be an ideal 'simple' system in which this aspect of NO function can be examined.