Inhibiting subthalamic D5 receptor constitutive activity alleviates abnormal electrical activity and reverses motor impairment in a rat model of Parkinson's disease

J Chetrit, A Taupignon, L Froux, S Morin… - Journal of …, 2013 - Soc Neuroscience
J Chetrit, A Taupignon, L Froux, S Morin, R Bouali-Benazzouz, F Naudet, N Kadiri, CE Gross…
Journal of Neuroscience, 2013Soc Neuroscience
Burst firing has been reported as a pathological activity of subthalamic nucleus (STN)
neurons in Parkinson9s disease. However, the origin of bursts and their causal link with
motor deficits remain unknown. Here we tested the hypothesis that dopamine D 5 receptors
(D 5 Rs), characterized by a high constitutive activity, may contribute to the emergence of
burst firing in STN. We tested whether inhibiting D 5 R constitutive activity depresses burst
firing and alleviates motor impairments in the 6-OHDA rat model of Parkinson9s disease …
Burst firing has been reported as a pathological activity of subthalamic nucleus (STN) neurons in Parkinson9s disease. However, the origin of bursts and their causal link with motor deficits remain unknown. Here we tested the hypothesis that dopamine D5 receptors (D5Rs), characterized by a high constitutive activity, may contribute to the emergence of burst firing in STN. We tested whether inhibiting D5R constitutive activity depresses burst firing and alleviates motor impairments in the 6-OHDA rat model of Parkinson9s disease. Intrasubthalamic microinjections of either an inverse agonist of D5Rs, flupenthixol, or a D2R antagonist, raclopride, were applied. Behavioral experiments, in vivo and in vitro electrophysiological recordings, and ex vivo functional neuroanatomy studies were performed. Using [5S]GTPγ binding autoradiography, we show that application of flupenthixol inhibits D5R constitutive activity within the STN. Furthermore, flupenthixol reduced evoked burst in brain slices and converted pathological burst firing into physiological tonic, single-spike firing in 6-OHDA rats in vivo. This later action was mimicked by calciseptine, a Cav1 channel blocker. Moreover, the same treatment dramatically attenuated motor impairment in this model and normalized metabolic hyperactivity in both STN and substantia nigra pars reticulata, the main output structure of basal ganglia in rats. In contrast, raclopride as well as saline did not reverse burst firing and motor deficits, confirming the selective action of flupenthixol on D5Rs. These results are the first to demonstrate that subthalamic D5Rs are involved in the pathophysiology of Parkinson9s disease and that administering an inverse agonist of these receptors may lessen motor symptoms.
Soc Neuroscience