The European journal of neuroscience
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Cellular expression of cytochrome oxidase subunit I (COI) mRNA has recently been used as a metabolic marker for neuronal activity to study the functional changes in the subthalamic nucleus (STN) in parkinsonism. The previous experimental studies have been performed when the pathological state was stabilized at a maximal level. In order to determine the evolution of changes in neuronal activity in the STN after nigrostriatal denervation, we analysed by in situ hybridization the cellular expression of COI mRNA in the subthalamic neurons at different times, from 6 h to 14 days, after unilateral intranigral microinjection of 6-hydroxydopamine (6-OHDA) in rats. ⋯ Similarly, electrical activity started to increase slightly 24 h after lesion (+20%) and remained significantly higher at 14 days after the lesion (+189%). Changes in neuronal mean discharge rate were associated with changes in the pattern of spiking activity, from a regular firing pattern to an irregular one with a high bursting activity. These results show that: (i) the hyperactivity of the STN represents a very early phenomenon in the physiopathology of parkinsonian syndromes; and (ii) that changes in COI mRNA expression slightly precede changes in electrical neuronal activity.
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Recent studies have suggested a role of connective tissue growth factor (CTGF) in repair processes of the skin as well as in various types of fibrotic disease. However, a function of this molecule in central nervous system (CNS) repair has not been demonstrated yet. ⋯ Interestingly, increased expression of this mitogen was accompanied by elevated levels of the extracellular matrix molecule fibronectin, which is a known target of CTGF action. Therefore, our data indicate a novel function of CTGF in postlesional restructuring of the hippocampus, where it possibly participates in glial scar formation.