We are interested in structural and functional neuronal plasticity of the insect nervous system. The nervous system is able to respond and adapt to a large variety of external factors during development and adult life, like environmental changes, injury, infection, or toxins, in order to ensure survival and reproduction of the animal. We are interested in the role of neuromodulatory transmitters in these adaptation processes, with a focus on biogenic amines (serotonin and octopamine), and the unusual gaseous transmitter nitric oxide (NO). In the following we will give some examples of our projects.

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Model organism locust, Locust brain, Locust embryo in tissue culture

Literature

Stern M (1999) Octopamine in the locust brain: Cellular distribution and functional significance in an arousal mechanism. Micr. Res. Tech. 45:135-141.

Stern M, Bicker G (2010) NO as a regulator of neuronal motility and regeneration in the locust nervous system. J. Insect Physiol. 56:958-965.

Bicker G, Stern M (2020) Structural and functional plasticity in the regenerating olfactory system of the migratory locust. Front. Physiol. 608661. doi: 10.3389/fphys.2020.608661

In a current DFG-funded project, we investigate the involvement of NO in neuro-immune interactions in collaboration with the group of Prof. Stephanie Becker, Institute of Parasitology. The objective is to elucidate possible implications of an infection (viral or bacterial) on the nervous system and behavior of insects, in particular the biting behavior of mosquitos carrying a pathogenic arbovirus. To this end, we measure NO-production in hemocytes, the insect’s immune cells, in response to pathogens, and quantify the behavior of infected vs. non-infected insects in a semi-automatic fashion.

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NO producing hemocytes (red) in cell culture, NO-synthase in mosquito brain

In a long-lasting project, we investigate the chemical neuroarchitecture of invertebrates as potential phylogenetic traits. In the last two decades, the use of molecular biological cues has led to major restructuring of phylogenetic trees, sometimes contradicting classical views based on morphology. Synaptic neurotransmitter equipment could provide additional independent information, here. Whereas vertebrates use acetylcholine (ACh) as the excitatory neuromuscular transmitter, insects and crustaceans use glutamate instead, with ACh as the transmitter of sensory neurons. In addition, several arthropods have GABAergic inhibitory motor neurons. We analyze a broad variety of arthropod and non-arthropod taxa in order to gain information about their motor and also sensory transmitters. We could show that the phylum Onychophora, at the base of the arthropod clade, uses both ACh and Glutamate as neuromuscular transmitters, and that centipedes have GABAergic sensory neurons.

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Onychophoran and recordings from its muscle Neuromuscular junctions (top) and sensory neurons (bottom) of a centipede

Literature

Stern M, Bicker G (2008) Mixed cholinergic/glutamatergic neuromuscular innervation of Onychophora: A combined histochemical/electrophysiological study. Cell Tissue Res. 333:333-338.

Langeloh H, Wasser H, Richter N, Bicker G, Stern M (2018) Neuromuscular transmitter candidates of a centipede (Lithobius forficatus, Chilopoda). Front. Zool. 15:28

In all projects, we offer Bachelor theses, Master 3. semester research modules and Master theses.

If you are interested, contact Michael.Stern(at)tiho-hannover.de