Odor transduction in the cilia of olfactory sensory neurons involves several ATP‐requiring enzymes. ATP is generated by glycolysis in the ciliary lumen, using glucose incorporated from surrounding mucus, and by oxidative phosphorylation in the dendrite. During prolonged stimulation, the cilia maintain ATP levels along their length, by unknown means. We used immunochemistry, RT‐PCR, and immunoblotting to explore possible underlying mechanisms. We found the ATP‐shuttles, adenylate and creatine kinases, capable of equilibrating ATP. We also investigated how glucose delivered by blood vessels in the olfactory mucosa reaches the mucus. We detected, in sustentacular and Bowman's gland cells, the crucial enzyme in glucose secretion glucose‐6‐phosphatase, implicating both cell types as putative glucose pathways. We propose a model accounting for both processes.

In several types of central mammalian synapses, sustained presynaptic stimulation leads to a sequence of two components of synaptic vesicle release, reflecting the consecutive contributions of a fast-releasing pool (FRP) and of a slow-releasing pool (SRP). Previous work has shown that following common depletion by a strong stimulation, FRP and SRP recover with different kinetics. However, it has remained unclear whether any manipulation could lead to a selective enhancement of either FRP or SRP. To address this question, we have performed local presynaptic calcium uncaging in single presynaptic varicosities of cerebellar interneurons. These varicosities typically form “simple synapses” onto postsynaptic interneurons, involving several (one to six) docking/release sites within a single active zone. We find that strong uncaging laser pulses elicit two phases of release with time constants of ∼1 ms (FRP release) and ∼20 ms (SRP release). When uncaging was preceded by action potential–evoked vesicular release, the extent of SRP release was specifically enhanced. We interpret this effect as reflecting an increased likelihood of two-step release (docking then release) following the elimination of docked synaptic vesicles by action potential–evoked release. In contrast, a subthreshold laser-evoked calcium elevation in the presynaptic varicosity resulted in an enhancement of the FRP release. We interpret this latter effect as reflecting an increased probability of occupancy of docking sites following subthreshold calcium increase. In conclusion, both fast and slow components of release can be specifically enhanced by certain presynaptic manipulations. Our results have implications for the mechanism of docking site replenishment and the regulation of synaptic responses, in particular following activation of ionotropic presynaptic receptors.

Schizophrenia (SZ) is a complex mental disease thought to arise from abnormal neurodevelopment, characterized by an altered reality perception and widely associated with brain connectivity anomalies. Previous work has shown disrupted resting-state brain functional connectivity (FC) in SZ patients. We used Human Induced Pluripotent Stem Cells (hiPSC)-derived neuronal cultures to study SZ's neural communicational dynamics during early development. We conducted gene and protein expression profiling, calcium imaging and mathematical modeling to evaluate FC. Along the neurodifferentiation process, SZ networks displayed altered expression of genes related to synaptic function, cell migration and cytoskeleton organization, suggesting alterations in excitatory/inhibitory balance. Resting-state FC in neuronal networks derived from healthy controls (HC) and SZ patients emerged as a dynamic phenomenon exhibiting "hub-states", which are connectivity configurations reoccurring in time. Compared to HC, SZ networks were less thorough in exploring different FC configurations, changed configurations less often, presented a reduced repertoire of hub-states and spent longer uninterrupted time intervals in this less diverse universe of hubs. Our observations at a single cell resolution may reflect intrinsic dynamical principles ruling brain activity at rest and highlight the relevance of identifying multiscale connectivity properties between functional brain units. We propose that FC alterations in SZ patients are a consequence of an abnormal early development of synaptic communication dynamics, compromising network's ability for rapid and efficient reorganization of neuronal activity patterns. Remarkably, these findings mirror resting-state brain FC in SZ patients, laying the groundwork for future studies among such different spatiotemporal domains, as are brains and neurons, in both health and disease.

One of the central goals of neuroscience is to decipher the specific contributions of neural mechanisms to different aspects of sensory perception. Since achieving this goal requires tools capable of precisely perturbing and monitoring neural activity across a multitude of spatiotemporal scales, this aim has inspired the innovation of many optical technologies capable of manipulating and recording neural activity in a minimally invasive manner. The interdisciplinary nature of neurophotonics requires a broad knowledge base in order to successfully develop and apply these technologies, and one of the principal aims of this chapter is to provide some basic but fundamental background information in terms of both physiology and optics in the context of all-optical two-photon neurophysiology experiments. Most of this information is expected to be familiar to readers experienced in either domain, but is presented here with the aim of bridging the divide between disciplines in order to enable physicists and engineers to develop useful optical technologies or for neuroscientists to select appropriate tools and apply them to their maximum potential.The first section of this chapter is dedicated to a brief overview of some basic principles of neural physiology relevant for controlling and recording neuronal activity using light. Then, the selection of appropriate actuators and sensors for manipulating and monitoring particular neural signals is discussed, with particular attention paid to kinetics and sensitivity. Some considerations for minimizing crosstalk in optical neurophysiology experiments are also introduced. Next, an overview of the state-of-the-art optical technologies is provided, including a description of suitable laser sources for two-photon excitation according to particular experimental requirements. Finally, some detailed, technical, information regarding the specific wavefront engineering approaches known as Generalized Phase Contrast (GPC) and temporal focusing is provided.