Localization of nitric oxide synthase in the central complex and surrounding midbrain neuropils of the locust Schistocerca gregaria

Abstract

Nitric oxide (NO), generated enzymatically by NO synthase (NOS), acts as an important signaling molecule in the nervous systems of vertebrates and invertebrates. In insects, NO has been implicated in development and in various aspects of sensory processing. To understand better the contribution of NO signaling to higher level brain functions, we analyzed the distribution of NOS in the midbrain of a model insect species, the locust Schistocerca gregaria, by using NADPH diaphorase (NADPHd) histochemistry after methanol/formalin fixation; results were validated by NOS immunohistochemistry. NADPHd yielded much higher sensitivity and resolution, but otherwise the two techniques resulted in corresponding labeling patterns throughout the brain, except for intense immunostaining but only weak NADPHd staining in median neurosecretory cells. About 470 neuronal cell bodies in the locust midbrain were NADPHd-positive positive, and nearly all major neuropil centers contained dense, sharply stained arborizations. We report several novel types of NOS-expressing neurons, including small ocellar interneurons and antennal sensory neurons that bypass the antennal lobe. Highly prominent labeling occurred in the central complex, a brain area involved in sky-compass orientation, and was analyzed in detail. Innervation by NOS-expressing fibers was most notable in the central body upper and lower divisions, the lateral accessory lobes, and the noduli. About 170 NADPHd-positive neurons contributed to this innervation, including five classes of tangential neuron, two systems of pontine neuron, and a system of columnar neurons. The results provide new insights into the neurochemical architecture of the central complex and suggest a prominent role for NO signaling in this brain area.

Distribution and characterization of nitric oxide synthase in the nervous system of Triatoma infestans (Insecta: Heteroptera)

“…Since no projections have been detected outside the glomeruli, we can hypothesize that NO release by these somata exerts a local action in the integration of sensory signals. The finding of NOS-LI in the antennal-mechanosensory and motor center of this triatomine bug is novel, as it has previously only been reported in S. gregaria (Kurylas et al 2005). In T. infestans, this immunolabeling might originate from positive somata surrounding this neuropil, as antennal afferents show no immunoreactivity.…”

Modeling Cooperative Volume Signaling in a Plexus of Nitric Oxide Synthase-Expressing Neurons

“…In the mammalian cerebral cortical plexus, NOS is clearly not confined to the synapse. The same applies to some hippocampal neurons (Burette et al, 2002) and to plexus neurons in invertebrate brains (Elphick et al, 1996;Ott and Burrows, 1998;Ott and Elphick, 2002;Kurylas et al, 2005). In all of these situations, even in neurons in which NOS is highly localized to the synapse, as NO will spread, significant cooperation between synapses is possible.…”

“…To optimize anatomical resolution further, a polyester wax preembedding technique was used in place of frozen sections. The protocol was given in detail previously (Kurylas et al, 2005). In brief, intact brains were stained en bloc and dehydrated following the whole-mount NADPHd protocol of Ott and Elphick (2003), infiltrated with polyester wax (BDH, Poole, UK) at 40°C (15 min each in 20, 40, 60, and 80% polyester wax in methanol and two times for 1 h pure polyester wax), and cut at 5-10 m. Sections were dewaxed in methanol and mounted in aqueous medium (Immu-Mount; Shandon, Pittsburgh, PA).…”

“…8 A) (cf. Kurylas et al, 2005). It is immediately evident that the precise branching morphology within each module is not fixed (i.e., not developmentally specified in detail), and we can safely assume that each instance of a plexus will generate different volume signals.…”

Nitric Oxide Synthase and NADPH Diaphorase Distribution in the Bullfrog <i>(Rana catesbeiana)</i> CNS: Pathways and Functional Implications

“…For example, NOS is present in the most primitive of metazoans, the sponges, as well as mollusks, annelids, cnidarians and arthropods [Leake and Moroz, 1996;Moroz and Gillette, 1996;Korneev et al, 1998;Giovine et al, 2001;Kitamura et al, 2001;Rast, 2001;Watson et al, 2001;Bullerjahn and Pfluger, 2003;Christie et al, 2003;Moroz et al, 2004;Kurylas et al, 2005]. NOS-immunoreactivity (NOS-ir) in non-mammalian vertebrate brains has been detected in various fishes [Brüning et al, 1995;Villani et al, 2001;Bordieri et al, 2003;Singru et al, 2003;Ando et al, 2004;Masini et al, 2005], reptiles [Brüning et al, 1994b;Smeets et al, 1997;Haverkamp et al, 2000], and birds [Brüning et al, 1994a;Garcia-Calero et al, 2002;Balthazart et al, 2003].…”