Our results suggest that PMSIs control the speed of axial locomotion by limiting, via inhibition, the duration of motor outputs in each segment. Similar mechanisms are found in the regulation of mammalian limb locomotion, suggesting that common strategies may be used to control the speed of animal movements in a diversity of species.

Neonicotinoid insecticides, which act on nicotinic acetylcholine receptors (nAChRs) in a variety of ways, have extremely low mammalian toxicity, yet the molecular basis of such actions is poorly understood. To elucidate the molecular basis for nAChR-neonicotinoid interactions, a surrogate protein, acetylcholine binding protein from Lymnaea stagnalis (Ls-AChBP) was crystallized in complex with neonicotinoid insecticides imidacloprid (IMI) or clothianidin (CTD). The crystal structures suggested that the guanidine moiety of IMI and CTD stacks with Tyr185, while the nitro group of IMI but not of CTD makes a hydrogen bond with Gln55. IMI showed higher binding affinity for Ls-AChBP than that of CTD, consistent with weaker CH-p interactions in the Ls-AChBP-CTD complex than in the Ls-AChBP-IMI complex and the lack of the nitro group-Gln55 hydrogen bond in CTD. Yet, the NH at position 1 of CTD makes a hydrogen bond with the backbone carbonyl of Trp143, offering an explanation for the diverse actions of neonicotinoids on nAChRs.

Mutations of the retromer component Vps35 and endosomal kinase LRRK2 are linked to autosomal dominant forms of familial Parkinson's disease (PD). However, the physiological and pathological roles of Vps35 and LRRK2 in neuronal functions are poorly understood. Here, we demonstrated that the loss of Drosophila Vps35 (dVps35) affects synaptic vesicle recycling, dopaminergic synaptic release and sleep behavior associated with dopaminergic activity, which is rescued by the expression of wild-type dVps35 but not the PD-associated mutant dVps35 D647N. Drosophila LRRK2 dLRRK together with Rab5 and Rab11 is also implicated in synaptic vesicle recycling, and the manipulation of these activities improves the Vps35 synaptic phenotypes. These findings indicate that defects of synaptic vesicle recycling in which two late-onset PD genes, Vps35 and LRRK2, are involved could be key aspects of PD etiology.

SUMMARY NMDA receptor (NMDAR) channels allow Ca2+ influx only during correlated activation of both pre- and postsynaptic cells; a Mg2+ block mechanism suppresses NMDAR activity when the postsynaptic cell is inactive. Although the importance of NMDARs in associative learning and long-term memory (LTM) formation has been demonstrated, the role of Mg2+ block in these processes remains unclear. Using transgenic flies expressing NMDARs defective for Mg2+ block, we found that Mg2+ block mutants are defective for LTM formation but not associative learning. We demonstrate that LTM-dependent increases in expression of synaptic genes, including homer, staufen, and activin, are abolished in flies expressing Mg2+ block defective NMDARs. Furthermore, we show that genetic and pharmacological reduction of Mg2+ block significantly increases expression of a CREB repressor isoform. Our results suggest that Mg2+ block of NMDARs functions to suppress basal expression of a CREB repressor, thus permitting CREB-dependent gene expression upon LTM induction.

Beta-amyloid precursor protein (APP) has been reported to be expressed in the CNS from the early stages of development. However, the functional role of APP during early development remains unclear. In the present study, we found that the secreted form of APP (sAPP) significantly enhanced proliferation of neural stem cells. Cells were prepared from 13-day embryonic rat neocortex, which was dissected with a Pasteur pipette to make cell clusters. After 12 h of cultivation in the medium without serum, cells around the centre of the cluster were still nestin-positive proliferative cells, i.e. neural stem cells. To determine whether the proliferation of cells was regulated by sAPP, cultures were treated with recombinant sAPP695, the secreted form of human APP695 produced by yeast. Both DNA synthesis and expression of proliferating cell nuclear antigen markedly increased after 5 h of sAPP695 addition. The enhancement of DNA synthesis by sAPP695 stimulation was blocked by the 22C11 monoclonal antibody specific for the amino-terminal region of sAPP. Then, we examined the effect of the amino-terminal fragment of sAPP and the epitope peptide of 22C11 antibody, and found that both of them also promoted DNA synthesis, suggesting that the amino-terminal region of sAPP is responsible for the biological activity. Our findings indicate the possibility that sAPP enhances proliferation of neural stem cells in vivo and plays an important role during the early CNS development.

1 ATP (10 ± 100 mM), but not glutamate (100 mM), stimulated the release of plasminogen from microglia in a concentration-dependent manner during a 10 min stimulation. However, neither ATP (100 mM) nor glutamate (100 mM) stimulated the release of NO. A one hour pretreatment with BAPTA-AM (200 mM), which is metabolized in the cytosol to BAPTA (an intracellular Ca 2+ chelator), completely inhibited the plasminogen release evoked by ATP (100 mM). The Ca 2+ ionophore A23187 induced plasminogen release in a concentration-dependent manner (0.3 mM to 10 mM). 2 ATP induced a transient increase in the intracellular calcium concentration ([Ca 2+ ] i ) in a concentration-dependent manner which was very similar to the ATP-evoked plasminogen release, whereas glutamate (100 mM) had no eect on [Ca ] i even at 1 mM, a concentration at which ATP did not evoke the increase. One hour pretreatment with adenosine 5'-triphosphate-2', 3'-dialdehyde (oxidized ATP, 100 mM), a selective antagonist of P2X 7 receptors, blocked the increase in [Ca 2+ ] i induced by ATP (10 and 100 mM). 4 These data suggest that ATP may transit information from neurones to microglia, resulting in an increase in [Ca 2+ ] i via the ionotropic P2X 7 receptor which stimulates the release of plasminogen from the microglia.

During courtship, many animals, including insects, birds, fish, and mammals, utilize acoustic signals to transmit information about species identity. Although auditory communication is crucial across phyla, the neuronal and physiologic processes are poorly understood. Sound-evoked chaining behavior, a display of homosexual courtship behavior in Drosophila males, has long been used as an excellent model for analyzing auditory behavior responses, outcomes of acoustic perception and higher-order brain functions. Here we developed a new method, termed ChaIN (Chain Index Numerator), in which we use a computer-based auto detection system for chaining behavior. The ChaIN system can systematically detect the chaining behavior induced by a series of modified courtship song playbacks. Two evolutionarily related Drosophila species, Drosophila melanogaster and Drosophila simulans, exhibited dramatic selective increases in chaining behavior when exposed to specific auditory cues, suggesting that auditory discrimination processes are involved in the acceleration of chaining behavior. Prolonged monotonous pulse sounds containing courtship song components also induced high intense chaining behavior. Interestingly, the chaining behavior was gradually suppressed over time when song playback continued. This behavioral change is likely to be a plastic behavior and not a simple sensory adaptation or fatigue, because the suppression was released by applying a different pulse pattern. This behavioral plasticity is not a form of habituation because different modality stimuli did not recover the behavioral suppression. Intriguingly, this plastic behavior partially depended on the cAMP signaling pathway controlled by the rutabaga adenylyl cyclase gene that is important for learning and memory. Taken together, this study demonstrates the selectivity and behavioral kinetics of the sound-induced interacting behavior of Drosophila males, and provides a basis for the systematic analysis of genes and neural circuits underlying complex acoustic behavior.

Following endocytic uptake of acetylcholine (ACh), CHO fibroblasts exhibit Ca(2+)-dependent spontaneous quantal ACh release and depolarization-evoked ACh release, as detected by a whole-cell voltage-clamped myocyte in contact with the fibroblast. CHO fibroblasts transfected with synaptotagmin I, an integral membrane protein of synaptic vesicles, showed a reduced spontaneous quantal ACh release and an enhanced Ca(2+)-evoked ACh release, as compared with control cells. Biochemical and ultrastructural studies of endocytic activity using horseradish peroxidase as a marker further confirmed the inhibitory action of synaptotagmin I on spontaneous vesicular exocytosis and on elevated exocytosis induced by Ca2+. Through inhibition of exocytosis at the resting intracellular concentration of Ca2+ and removal of the inhibition upon depolarization-induced Ca2+ entry, synaptotagmin I could enhance the efficiency of excitation-secretion coupling.