Abnormalities of cerebral white matter, oligodendrocytes, and myelin have been observed in schizophrenia with in-vivo imaging and post-mortem biochemistry. White-matter abnormalities are also frequently associated with cognitive impairment in both healthy and diseased individuals, and cognitive dysfunction is an important component of schizophrenia. While many studies have documented these associations, only a handful have examined the role of white matter in cognitive function in schizophrenia. In this paper, we explore what is known about white-matter deficits in relation to schizophrenia, cognitive deficits, or both together, in order to generate a theoretical model for the role that compromise of white matter might play in producing cognitive impairment in schizophrenia.

Abnormalities of amount and function of presynaptic terminals may have an important role in the mechanism of illness in schizophrenia. The SNARE proteins (SNAP-25, syntaxin, and VAMP) are enriched in presynaptic terminals, where they interact to form a functional complex to facilitate vesicle fusion. SNARE protein amounts are altered in the cortical regions in schizophrenia, but studies of proteinprotein interactions are limited. We extended these investigations to the striatal regions (such as the nucleus accumbens, ventromedial caudate (VMC), and dorsal caudate) relevant to disease symptoms. In addition to measuring SNARE protein levels, we studied SNARE protein-protein interactions using a novel ELISA method. The possible effect of antipsychotic treatment was investigated in parallel in the striatum of rodents that were administered haloperidol and clozapine. In schizophrenia samples, compared with controls, SNAP-25 was 32% lower (P ¼ 0.015) and syntaxin was 26% lower (P ¼ 0.006) in the VMC. In contrast, in the same region, SNARE protein-protein interactions were higher in schizophrenia (P ¼ 0.008). Confocal microscopy of schizophrenia and control VMC showed qualitatively similar SNARE protein immunostaining. Haloperidol treatment of rats increased levels of SNAP-25 (mean 24%, P ¼ 0.003), syntaxin (mean 18%, P ¼ 0.010), and VAMP (mean 16%, P ¼ 0.001), whereas clozapine increased only the VAMP level (mean 13%, P ¼ 0.004). Neither drug altered SNARE protein-protein interactions. These results indicate abnormalities of amount and interactions of proteins directly related to presynaptic function in the VMC in schizophrenia. SNARE proteins and their interactions may be a novel target for the development of therapeutics.

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