title: HCN2 and HCN1 channels govern the regularity of autonomous pacemaking and synaptic resetting in globus pallidus neurons.
abstract: The globus pallidus (GP) is a critical component of the basal ganglia circuitry controlling motor behavior. Dysregulation of GP activity has been implicated in a number of psychomotor disorders, including Parkinson's disease (PD), in which a cardinal feature of the pathophysiology is an alteration in the pattern and synchrony of discharge in GP neurons. Yet the determinants of this activity in GP neurons are poorly understood. To help fill this gap, electrophysiological, molecular, and computational approaches were used to identify and characterize GABAergic GP neurons in tissue slices from rodents. In vitro, GABAergic GP neurons generate a regular, autonomous, single-spike pacemaker activity. Hyperpolarization-activated, cyclic nucleotide-gated cation (HCN) channels make an important contribution to this process: their blockade with ZD7288 significantly slowed discharge rate and decreased its regularity. HCN currents evoked by somatic voltage clamp had fast and slow components. Single-cell RT-PCR and immunohistochemical approaches revealed robust expression of HCN2 subunits as well as significant levels of HCN1 subunits in GABAergic GP neurons. Transient activation of striatal GABAergic input to GP neurons led to a resetting of rhythmic discharge that was dependent on HCN currents. Simulations suggested that the ability of transient striatal GABAergic input to reset pacemaking was dependent on dendritic HCN2/HCN1 channels. Together, these studies show that HCN channels in GABAergic GP neurons are key determinants of the regularity and rate of pacemaking as well as striatal resetting of this activity, implicating HCN channels in the emergence of synchrony in PD.
authors.affiliation: Department of Physiology and Institute for Neuroscience, Feinberg School of Medicine, Northwestern University, Chicago, Illinois 60611, USA.
authors.forename: C Savio
authors.initials: CS
authors.lastname: Chan
authors.forename: Ryuichi
authors.initials: R
authors.lastname: Shigemoto
authors.forename: Jeff N
authors.initials: JN
authors.lastname: Mercer
authors.forename: D James
authors.initials: DJ
authors.lastname: Surmeier
mesh_terms: D000200:Action Potentials / Q000502:physiology*; D000818:Animals; D001683:Biological Clocks / Q000502:physiology; D020747:Calcium Channels, T-Type / Q000502:physiology; D003342:Corpus Striatum / Q000502:physiology; D054815:Cyclic Nucleotide-Gated Cation Channels; D005260:Female; D005917:Globus Pallidus / Q000166:cytology / Q000502:physiology*; D064428:Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels; D066298:In Vitro Techniques; D007473:Ion Channels / Q000502:physiology*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008959:Models, Neurological; D009419:Nerve Tissue Proteins / Q000502:physiology*; D009434:Neural Pathways / Q000502:physiology; D009474:Neurons / Q000502:physiology*; D015221:Potassium Channels; D051381:Rats; D017207:Rats, Sprague-Dawley; D013569:Synapses / Q000502:physiology*; D013997:Time Factors; D005680:gamma-Aminobutyric Acid / Q000502:physiology
chemical_list: D020747:Calcium Channels, T-Type; D054815:Cyclic Nucleotide-Gated Cation Channels; C578666:Hcn1 protein, mouse; C578667:Hcn1 protein, rat; C578711:Hcn2 protein, mouse; C578712:Hcn2 protein, rat; D064428:Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels; D007473:Ion Channels; D009419:Nerve Tissue Proteins; D015221:Potassium Channels; D005680:gamma-Aminobutyric Acid