IP Nervous

Nitric oxide: An unconventional transmitter in insect nervous systems

G. Bicker, O. Schmachtenberg, C. Seidel & B. Wildemann

Institut für und Tierökologie und Zellbiologie, Tierärztliche Hochschule Hannover, Bünteweg 17d, D-30559 Hannover, Germany

In nerve cells, the short-lived signalling molecule nitric oxide (NO) is generated by Ca2+/calmodulin stimulated NO synthases (NOS). NO activates soluble guanylyl cyclase (sGC) in target cells leading to the formation of cGMP. Using NADPH-diaphorase (NADPHd) staining as a marker for the enzyme nitric oxide synthase and an antiserum against cGMP, the cellular organisation of NO donor and target cells has been resolved in the locust and fruit fly. In this seminar, I will attempt to provide an overview about the cellular organization of NO signalling as well as to highlight some of its functions in vision, neuromuscular transmission, and neuronal development. Cytochemical stainings and electrophysiological experiments suggest that NO is a retrograde messer in the visual system of the locust. Using a fluorescent dye that is known to stain recycling synaptic vesicles it was demonstrated that NO donors and membrane permeant cGMP analogues cause vesicle release at the neuromuscular junction of Drosophila. The combined immunocytochemical and exocytosis imaging experiments imply the involvement of cGMP and NO in the regulation of vesicle release during the maturation of the larval NMJ. During the formation of the grasshopper nervous system, antennal pioneer neurons synthesize cGMP in response to NO stimulation To investigate a potential role of the NO/cGMP signaling system in axonal extension, the pattern of outgrowing pioneer neurons was examined in embryo culture. Axogenesis of both pairs of antennal pioneers is inhibited when specific NOS or sGC blockers were added to the culture medium; the observed effects include the loss axon emergence as well as retardation of outgrowth such that growth cones do not reach the CNS. These results indicate that NO/cGMP signaling is involved in axonal navigation of pioneer neurons in the antenna of the grasshopper.

Index terms: Drosophila, Schistocerca, cGMP, development, synapse

Copyright: The copyrights of this work belong to the author (see right-most box of the title table). It also appears in Session 13 - INSECT PHISIOLOGY, NEUROSCIENCES, IMMUNITY AND CELL BIOLOGY Symposium and Poster Session, ABSTRACT BOOK II – XXI-International Congress of Entomology, Brazil, August 20-26, 2000.