title: Differential excitability and modulation of striatal medium spiny neuron dendrites.
abstract: The loss of striatal dopamine (DA) in Parkinson's disease (PD) models triggers a cell-type-specific reduction in the density of dendritic spines in D(2) receptor-expressing striatopallidal medium spiny neurons (D(2) MSNs). How the intrinsic properties of MSN dendrites, where the vast majority of DA receptors are found, contribute to this adaptation is not clear. To address this question, two-photon laser scanning microscopy (2PLSM) was performed in patch-clamped mouse MSNs identified in striatal slices by expression of green fluorescent protein (eGFP) controlled by DA receptor promoters. These studies revealed that single backpropagating action potentials (bAPs) produced more reliable elevations in cytosolic Ca(2+) concentration at distal dendritic locations in D(2) MSNs than at similar locations in D(1) receptor-expressing striatonigral MSNs (D(1) MSNs). In both cell types, the dendritic Ca(2+) entry elicited by bAPs was enhanced by pharmacological blockade of Kv4, but not Kv1 K(+) channels. Local application of DA depressed dendritic bAP-evoked Ca(2+) transients, whereas application of ACh increased these Ca(2+) transients in D(2) MSNs, but not in D(1) MSNs. After DA depletion, bAP-evoked Ca(2+) transients were enhanced in distal dendrites and spines in D(2) MSNs. Together, these results suggest that normally D(2) MSN dendrites are more excitable than those of D(1) MSNs and that DA depletion exaggerates this asymmetry, potentially contributing to adaptations in PD models.
authors.affiliation: Department of Physiology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois 60611, USA.
authors.forename: Michelle
authors.initials: M
authors.lastname: Day
authors.forename: David
authors.initials: D
authors.lastname: Wokosin
authors.forename: Joshua L
authors.initials: JL
authors.lastname: Plotkin
authors.forename: Xinyoung
authors.initials: X
authors.lastname: Tian
authors.forename: D James
authors.initials: DJ
authors.lastname: Surmeier
mesh_terms: D000200:Action Potentials / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects; D000704:Analysis of Variance; D000820:Animal Diseases; D000818:Animals; D000831:Animals, Newborn; D002118:Calcium / Q000378:metabolism; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000166:cytology; D018920:Coculture Techniques / Q000379:methods; D003198:Computer Simulation; D003342:Corpus Striatum / Q000473:pathology*; D003712:Dendrites / Q000473:pathology / Q000502:physiology*; D049452:Green Fluorescent Proteins / Q000378:metabolism; D051379:Mice; D008822:Mice, Transgenic; D018613:Microscopy, Confocal / Q000379:methods; D008959:Models, Neurological; D009474:Neurons / Q000145:classification / Q000473:pathology / Q000648:ultrastructure; D010300:Parkinson Disease / Q000235:genetics / Q000473:pathology; D018408:Patch-Clamp Techniques / Q000379:methods; D017447:Receptors, Dopamine D1 / Q000235:genetics; D017448:Receptors, Dopamine D2 / Q000235:genetics; D013569:Synapses / Q000187:drug effects / Q000502:physiology
chemical_list: D017447:Receptors, Dopamine D1; D017448:Receptors, Dopamine D2; D049452:Green Fluorescent Proteins; D002118:Calcium