Current schizophrenia (SCZ) treatments fail to treat the broad range of manifestations associated with this devastating disorder. Thus, new translational models that reproduce the core pathological features are urgently needed to facilitate novel drug discovery efforts. Here, we report findings from the first comprehensive label-free liquid-mass spectrometry proteomic-and proton nuclear magnetic resonance-based metabonomic profiling of the rat frontal cortex after chronic phencyclidine (PCP) intervention, which induces SCZ-like symptoms. The findings were compared with results from a proteomic profiling of post-mortem prefrontal cortex from SCZ patients and with relevant findings in the literature. Through this approach, we identified proteomic alterations in glutamate-mediated Ca 2 þ signaling (Ca 2 þ /calmodulin-dependent protein kinase II, PPP3CA, and VISL1), mitochondrial function (GOT2 and PKLR), and cytoskeletal remodeling (ARP3). Metabonomic profiling revealed changes in the levels of glutamate, glutamine, glycine, pyruvate, and the Ca 2 þ regulator taurine. Effects on similar pathways were also identified in the prefrontal cortex tissue from human SCZ subjects. The discovery of similar but not identical proteomic and metabonomic alterations in the chronic PCP rat model and human brain indicates that this model recapitulates only some of the molecular alterations of the disease. This knowledge may be helpful in understanding mechanisms underlying psychosis, which, in turn, can facilitate improved therapy and drug discovery for SCZ and other psychiatric diseases. Most importantly, these molecular findings suggest that the combined use of multiple models may be required for more effective translation to studies of human SCZ.

Peripheral neuropathy (PN) is the most common complication of prediabetes and diabetes. PN causes severe morbidity for Type 2 diabetes (T2D) and prediabetes patients, including limb pain followed by numbness resulting from peripheral nerve damage. PN in T2D and prediabetes is associated with dyslipidemia and elevated circulating lipids; however, the molecular mechanisms underlying PN development in prediabetes and T2D are unknown. Peripheral nerve sensory neurons rely on axonal mitochondria to provide energy for nerve impulse conduction under homeostatic conditions. Models of dyslipidemia in vitro demonstrate mitochondrial dysfunction in sensory neurons exposed to elevated levels of exogenous fatty acids. Herein, we evaluated the effect of dyslipidemia on mitochondrial function and dynamics in sensory axons of the saphenous nerve of a male high-fat diet (HFD)-fed murine model of prediabetes to identify mitochondrial alterations that correlate with PN pathogenesis in vivo. We found that the HFD decreased mitochondrial membrane potential (MMP) in axonal mitochondria and reduced the ability of sensory neurons to conduct at physiological frequencies. Unlike mitochondria in control axons, which dissipated their MMP in response to increased impulse frequency (from 1 to 50 Hz), HFD mitochondria dissipated less MMP in response to axonal energy demand, suggesting a lack of reserve capacity. The HFD also decreased sensory axonal Ca 21 levels and increased mitochondrial lengthening and expression of PGC1a, a master regulator of mitochondrial biogenesis. Together, these results suggest that mitochondrial dysfunction underlies an imbalance of axonal energy and Ca 21 levels and impairs impulse conduction within the saphenous nerve in prediabetic PN.

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The previous chapters have described the extraordinary depth of knowledge of mitochondrial biology revealed by in vitro observations where the environment can be closely controlled. However, in recent years there has been increased interest in the study of mitochondria in vivo, where their properties can be studied with high spatial and temporal resolution while ensuring that key factors such as the oxygen and glucose concentrations are physiologically accurate. Advances facilitating such in vivo research include improved microscope systems and mitochondrially targeted dyes, as well as a wide range of transgenic animals expressing fl uorescent proteins. Such in vivo observations provide a more realistic picture of mitochondrial involvement in health and disease and also offer the potential to reveal novel targets for therapeutic interventions. For example, loss of mitochondrial membrane potential and alterations in mitochondrial morphology and traffi cking have been reported in mouse models of multiple sclerosis and Alzheimer's disease, and redox potential changes have been reported during (patho)physiological changes in oxygen supply and demand.In this chapter we summarise some techniques used in imaging of mitochondria in vivo, followed by a summary of key fi ndings and recent advances in the study of mitochondrial function and dynamics. We aim to provide insight into the benefi ts and limitations of intravital imaging of mitochondria in the nervous system.