Subcellular distribution of high-voltage-activated calcium channel subtypes in rat globus pallidus neurons.
Globus pallidus (GP) neurons receive dense inhibitory synaptic inputs interspersed with sparse excitatory inputs distributed across the entire extent of their somata and dendrites. Yet, despite this predominance of inhibitory influence, GP neurons fire at a high tonic rate, suggesting that intrinsic properties play an important role in determining the physiological characteristics of these neurons. High-voltage-activated (HVA) calcium channels represent an important class of conductances that plays roles in controlling neurotransmitter release, postsynaptic excitability, and intracellular calcium signaling. To better understand the intrinsic properties of GP neurons, we examined the subcellular localization of HVA calcium channels by using immunocytochemistry at the electron microscopic level. Peroxidase labeling with antibodies against P/Q-, N-, and R-type HVA calcium channels demonstrated the presence of these channels in both proximal and distal dendrites of GP neurons. P/Q-, N-, and R-type channels were also found in presynaptic terminals, whereas L-type channels were found exclusively postsynaptically in neuronal elements. Immunogold labeling demonstrated that, although the density of intracellular L-type calcium channel labeling remains constant throughout the proximal-distal extent of the dendritic tree of GP neurons, the density of plasma membrane-bound channels is greater in distal dendrites. The finding of HVA calcium channels distributed throughout the whole dendritic tree of GP neurons indicates that these channels may interact with synaptic inputs to allow rich processing possibilities for GP neuron dendrites. Furthermore, the finding of a greater density of plasma membrane-bound L-type channels in distal dendrites expands the view that L-type channels are important only in somatic and proximal locations.
Hanson
Jesse E
JE
Yerkes Regional Primate Research Center, Division of Neuroscience and Department of Neurology, Emory University, Atlanta, Georgia 30322, USA.
Smith
Yoland
Y
D000818:Animals; D015220:Calcium Channels / Q000378:metabolism* / Q000648:ultrastructure; D020864:Calcium Channels, N-Type / Q000378:metabolism / Q000648:ultrastructure; D020865:Calcium Channels, P-Type / Q000378:metabolism / Q000648:ultrastructure; D020908:Calcium Channels, R-Type / Q000378:metabolism / Q000648:ultrastructure; D002451:Cell Compartmentation / Q000502:physiology; D002462:Cell Membrane / Q000378:metabolism* / Q000648:ultrastructure; D003593:Cytoplasm / Q000378:metabolism / Q000648:ultrastructure; D003712:Dendrites / Q000378:metabolism* / Q000648:ultrastructure; D005917:Globus Pallidus / Q000378:metabolism* / Q000648:ultrastructure; D007150:Immunohistochemistry; D008854:Microscopy, Electron; D017729:Presynaptic Terminals / Q000378:metabolism* / Q000648:ultrastructure; D051381:Rats; D017207:Rats, Sprague-Dawley; D013570:Synaptic Membranes / Q000378:metabolism* / Q000648:ultrastructure; D009435:Synaptic Transmission / Q000502:physiology*
D015220:Calcium Channels; D020864:Calcium Channels, N-Type; D020865:Calcium Channels, P-Type; D020908:Calcium Channels, R-Type