Metabolic dysfunction as a consequence of
thiamine (
vitamin B1) deficiency (TD), a model of
Wernicke's encephalopathy, leads to elevation of extracellular
glutamate concentration in vulnerable brain regions consistent with the development of excitotoxicity.
Complexin I and
complexin II are two genes labeling principally inhibitory and excitatory synapses, respectively. Because current evidence supports an important role for complexins in the modulation of
neurotransmitter release, we examined the involvement of both
proteins in the pathology of the medial thalamus and inferior colliculus in TD rats by immunoblotting. At the symptomatic stage,
complexin I and
complexin II levels in the medial thalamus were decreased by 63% and 45%, respectively, compared to control animals, but were unchanged in the inferior colliculus. These changes in thalamus were also observed using immunohistochemical methods, and seemed to be due to downregulation of both
proteins because
synaptophysin levels were unaffected in this brain region. In addition, cotreatment with the
antioxidant N- acetylcysteine prevented both neuronal loss and downregulation of complexins. Our findings suggest dysregulation of excitatory and inhibitory
neurotransmitter release in the medial thalamus, which is not present in the inferior colliculus. Furthermore, loss of
complexin I and II in the thalamus may be mediated by processes that involve oxidative stress. Such changes in complexin levels may contribute to the pathophysiology of thalamic damage in TD, and offer a potential basis for the well-known differences in pathology between this structure and the inferior colliculus in this disorder.