Perisomatic inhibition provided by a subgroup of GABAergic interneurons plays a critical role in timing the output of pyramidal cells. To test their contribution at the network and the behavioral level, we generated genetically modified mice in which the excitatory drive was selectively reduced either by the knockout of the GluR-D or by conditional ablation of the GluR-A subunit in parvalbumin-positive cells. Comparable cell type-specific reductions of AMPA-mediated currents were obtained. Kainate-induced gamma oscillations exhibited reduced power in hippocampal slices from GluR-D-/- and GluR-A(PVCre-/-) mice. Experimental and modeling data indicated that this alteration could be accounted for by imprecise spike timing of fast-spiking cells (FS) caused by smaller interneuronal EPSPs. GluR-D-/- and GluR-A(PVCre-/-) mice exhibited similar impairments in hippocampus-dependent tasks. These findings directly show the effects of insufficient recruitment of fast-spiking cells at the network and behavioral level and demonstrate the role of this subpopulation for working and episodic-like memory.

Summary Intracellular transport regulates protein turnover including endocytosis. Because of the spatial segregation of F-actin and microtubules, internalized cargo vesicles need to employ retrograde myosin and dynein motors to traverse both cytoskeletal compartments. Factors specifying cargo delivery across both tracks remain unknown. We identified muskelin to interconnect retrograde F-actin- and microtubule-dependent GABAA receptor (GABAAR) trafficking. GABAARs regulate synaptic transmission, plasticity, and network oscillations. GABAAR α1 and muskelin interact directly, undergo neuronal cotransport, and associate with myosin VI or dynein motor complexes in subsequent steps of GABAAR endocytosis. Inhibition of either transport route selectively interferes with receptor internalization or degradation. Newly generated muskelin KO mice display depletion of both transport steps and a high-frequency ripple oscillation phenotype. A diluted coat color of muskelin KOs further suggests muskelin transport functions beyond neurons. Our data suggest the concept that specific trafficking factors help cargoes to traverse both F-actin- and microtubule compartments, thereby regulating their fate.

Systemic inflammation is an immune response to a nonspecific insult of either infectious or noninfectious origin and remains a challenge in the intensive care units with high mortality rate. Cholinergic neurotransmission plays an important role in the regulation of the immune response during inflammation. We hypothesized that the activity of butyrylcholinesterase (BChE) might serve as a marker to identify and prognose systemic inflammation. By using a point-of-care-testing (POCT) approach we measured BChE activity in patients with severe systemic inflammation and healthy volunteers. We observed a decreased BChE activity in patients with systemic inflammation, as compared to that of healthy individuals. Furthermore, BChE activity showed an inverse correlation with the severity of the disease. Although hepatic function has previously been found essential for BChE production, we show here that the reduced BChE activity associated with systemic inflammation occurs independently of and is thus not caused by any deficit in liver function in these patients. A POCT approach, used to assess butyrylcholinesterase activity, might further improve the therapy of the critically ill patients by minimizing time delays between the clinical assessment and treatment of the inflammatory process. Hence, assessing butyrylcholinesterase activity might help in early detection of inflammation.