Neuronal calcium acts as a charge carrier during information processing and as a ubiquitous intracellular messenger. Calcium signals are fundamental to numerous aspects of neuronal development and plasticity. Specific and independent regulation of these vital cellular processes is achieved by a rich bouquet of different calcium signaling mechanisms within the neuron, which either can operate independently or may act in concert. This study demonstrates the existence of a novel calcium signaling mechanism by simultaneous patch clamping and calcium imaging from acutely isolated central neurons. These neurons possess a membrane voltage sensor that, independent of calcium influx, causes G-protein activation, which subsequently leads to calcium release from intracellular stores via phospholipase C and inositol 1,4,5-trisphosphate receptor activation. This allows neurons to monitor activity by intracellular calcium release without relying on calcium as the input signal and opens up new insights into intracellular signaling, developmental regulation, and information processing in neuronal compartments lacking calcium channels.

30Interactions among different neuronal circuits are essential for adaptable 31 coordinated behavior. Specifically, higher motor centers and central pattern generators 32 (CPGs) induce rhythmic leg movements that act in concert in the control of locomotion. 33Here we explored the relations between the subesophageal ganglion (SEG) and thoracic 34 leg CPGs in the desert locust. Backfill staining revealed about 300 SEG descending 35 interneurons (DINs) and some overlap with the arborization of DINs and leg motor 36 neurons. In accordance, in in-vitro preparations, electrical stimulation applied to the SEG 37 excited these neurons, and in some cases also induced CPGs activity. Additionally, we 38 found that the SEG regulates the coupling pattern among the CPGs: when the CPGs were 39 activated pharmacologically, inputs from the SEG were able to synchronize contralateral 40CPGs. This motor output was correlated to the firing of SEG descending and local 41 interneurons. Altogether, these findings point to a role of the SEG in both activating leg 42CPGs and in coordinating their oscillations, and suggest parallels between the SEG and 43 the brainstem of vertebrates. 44 45 46

Activation and modulation of sensory-guided behaviors by biogenic amines assure appropriate adaptations to changes in an insect's environment. Given its genetic tool kit Drosophila melanogaster represents an excellent model organism to study larger networks of neurons by optophysiological methods. Here, we studied stationary crawling movements of 3rd instar larvae and revealed how the octopaminergic VUM neuron system reacts during crawling behavior and tactile stimulations. We conducted calcium imaging experiments on dissections of the isolated nervous system (missing all sensory input) and found spontaneous rhythmic wave pattern of neuronal activity in VUM neuron clusters over the range of thoracic and abdominal neuromeres in the VNC. In contrast, in vivo preparations (semi-intact animals, receiving sensory input) did not reveal such spontaneous rhythmic pattern. However, tactile stimulations activated different clusters of the VUM neuron system simultaneously in these preparations. The activation intensity of VUM neurons in the VNC was correlated with the location and degree of body wall stimulation. While VUM neuron cluster near the respective location of body wall stimulation were less activated more distant cluster showed stronger activation. Repeated gentle touch stimulations led to decreased response intensities, repeated harsh stimulations resulted in increasing intensities over trials. Optophysiological signals correlated highly with crawling behavior in freely moving larvae stimulated similarly. We conclude that the octopaminergic system is strongly coupled to the neuronal pattern generator of crawling movements and that it is simultaneously activated by physical stimulation, rather intensity than sequential coded. We hope that our work raises the interest in whole biogenic network activity and shows that octopamine release does not only underlie "the more the better" principle but instead has a more complex function in control and modulation of insect's locomotion.