Abnormal neuronal activity in the subthalamic nucleus (STN) plays a crucial role in the pathophysiology of Parkinson's disease (PD). In this study we investigated changes in rat STN neuronal activity after 28 days following the injection of 6-OHDA in the substantia nigra pars compacta (SNc). This drug provoked a lesion of SNc that induced a dopamine and lesioned (n = 83) groups was similar, as well as the firing rate. In 6-OHDA treated rats we observed a significant increase (from 26% to 48%) in the number of pairs with synchronous firing. These data suggest that the synchronous activity of STN cells, provoked by loss of DA cells in SNc, is likely to be among the most significant dysfunctions in the basal ganglia of Parkinsonian patients. We raise the hypothesis that in normal conditions, DA maintains a balance between funneling information via the hyperdirect cortico-subthalamic pathway and parallel processing through the parallel cortico-basal ganglia-subthalamic pathways, both of which are necessary for selected motor behaviors..
Long-term potentiation (LTP) and long-term depression (LTD) of the efficiency of inhibitory transmission between different elements of a network took place in neuronal networks consisting of AC and MGB cells, as a result of MS of the cortex. LTP of inhibition was an input-specific effect, since it could develop simultaneously with LTP of the efficiency of excitatory transmission to the same cell and do not lead to a decrease in its baseline frequency. LTP (LTD) of inhibition was observed simultaneously with an increase (decrease) in the frequency of baseline impulse activity of the inhibitory neuron or neuron which is presynaptic in relation to an inhibitory neuron; the efficiency of the synaptic effect of one inhibitory neuron on various postsynaptic cells could vary in different directions. The data obtained may suggest the participation of both pre- and postsynaptic mechanisms in the modification of the efficiency of inhibition.
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