STN Activity Recorded in Vitro: Brain Slices
From in vivo experimental studies in monkeys it was found that the neurons of the subthalamic nucleus perform a dual function: (1) they discharge continuously and repetitively at low frequencies (10–30 Hz) in the awake resting state and (2) they discharge bursts of high-frequency spikes (up to several hundred per second), which can last up to 100 ms before, during, and after limb or eye movements in the awake state. The latter activity patterns in turn increase the activity of basal ganglia output neurons and are likely to suppress non-selected motor programmes or terminate sequences of motor behaviour.
In normal monkeys, lesioning of the STN, pharmacologically blocking STN activity or high-frequency stimulation produces a hyperkinetic syndrome (Beurrier et al. 1999). However, in MPTP-treated monkeys, which model Parkinson's disease, these methods show a reduction in motor impairment. In order to gain more insight into the regulation of the basal ganglia by the subthalamic nucleus, it is essential to investigate the underlying ionic mechanisms. In vitro brain slice studies as well as dissociated cell cultures provide a means to (partly) open the closed-loop system of the basal ganglia and to determine the types of membrane channels that are responsible for the regulating behaviour of the STN.
Nakanishi et al. (1987) describe one of the first intracellular recordings from STN neurons in brain slices. Later, a number of investigators added new information by focussing on the plateau potential and low-frequency spikes that were recorded in brain slices and/or acutely dissociated STN neurons. A summary of the results of several studies is described in this section. Details of culturing procedures can be found in the references given.
KeywordsBrain Slice Rest Membrane Potential Spontaneous Firing Plateau Potential Burst Firing
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