Increasing extracellular potassium results in subthalamic neuron activity resembling that seen in a 6-hydroxydopamine lesion.
Journal of Neurophysiology. 2008-06-01; 99(6): 2902-2915
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1. J Neurophysiol. 2008 Jun;99(6):2902-15. doi: 10.1152/jn.00402.2007. Epub 2008 Apr
Increasing extracellular potassium results in subthalamic neuron activity
resembling that seen in a 6-hydroxydopamine lesion.
Strauss U(1), Zhou FW, Henning J, Battefeld A, Wree A, Köhling R, Haas SJ,
Benecke R, Rolfs A, Gimsa U.
(1)Neurobiology, Department of Neurology, University of Rostock, Rostock,
Abnormal neuronal activity in the subthalamic nucleus (STN) plays a crucial role
in the pathophysiology of Parkinson’s disease (PD). Although altered
extracellular potassium concentration ([K+]o) and sensitivity to [K+]o modulates
neuronal activity, little is known about the potassium balance in the healthy and
diseased STN. In vivo measurements of [K+]o using ion-selective electrodes
demonstrated a twofold increase in the decay time constant of lesion-induced
[K+]o transients in the STN of adult Wistar rats with a unilateral
6-hydroxydopamine (6-OHDA) median forebrain bundle lesion, employed as a model of
PD, compared with nonlesioned rats. Various [K+]o concentrations (1.5-12.5 mM)
were applied to in vitro slice preparations of three experimental groups of STN
slices from nonlesioned control rats, ipsilateral hemispheres, and contralateral
hemispheres of lesioned rats. The majority of STN neurons of nonlesioned rats and
in slices contralateral to the lesion fired spontaneously, predominantly in a
regular pattern, whereas those in slices ipsilateral to the lesion fired more
irregularly or even in bursts. Experimentally increased [K+]o led to an increase
in the number of spontaneously firing neurons and action potential firing rates
in all groups. This was accompanied by a decrease in the amplitude of post spike
afterhyperpolarization (AHP) and the amplitude and duration of the posttrain AHP.
Lesion effects in ipsilateral neurons at physiological [K+]o resembled the
effects of elevated [K+]o in nonlesioned rats. Our data suggest that changed
potassium sensitivity due to conductivity alterations and delayed clearance may
be critical for shaping STN activity in parkinsonian states.
PMID: 18385482 [Indexed for MEDLINE]