D2-like dopamine receptors modulate SKCa channel function in subthalamic nucleus neurons through inhibition of Cav2.2 channels.
The activity patterns of subthalamic nucleus (STN) neurons are intimately related to motor function/dysfunction and modulated directly by dopaminergic neurons that degenerate in Parkinson's disease (PD). To understand how dopamine and dopamine depletion influence the activity of the STN, the functions/signaling pathways/substrates of D2-like dopamine receptors were studied using patch-clamp recording. In rat brain slices, D2-like dopamine receptor activation depolarized STN neurons, increased the frequency/irregularity of their autonomous activity, and linearized/enhanced their firing in response to current injection. Activation of D2-like receptors in acutely isolated neurons reduced transient outward currents evoked by suprathreshold voltage steps. Modulation was inhibited by a D2-like receptor antagonist and occluded by voltage-dependent Ca2+ (Cav) channel or small-conductance Ca2+-dependent K+ (SKCa) channel blockers or Ca2+-free media. Because Cav channels are targets of G(i/o)-linked receptors, actions on step- and action potential waveform-evoked Cav channel currents were studied. D2-like receptor activation reduced the conductance of Cav2.2 but not Cav1 channels. Modulation was mediated, in part, by direct binding of Gbetagamma subunits because it was attenuated by brief depolarization. D2 and/or D3 dopamine receptors may mediate modulation because a D4-selective agonist was ineffective and mRNA encoding D2 and D3 but not D4 dopamine receptors was detectable. Brain slice recordings confirmed that SKCa channel-mediated action potential afterhyperpolarization was attenuated by D2-like dopamine receptor activation. Together, these data suggest that D2-like dopamine receptors potently modulate the negative feedback control of firing that is mediated by the functional coupling of Cav2.2 and SKCa channels in STN neurons.
Ramanathan
Sankari
S
Department of Physiology, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA.
Tkatch
Tatiana
T
Atherton
Jeremy F
JF
Wilson
Charles J
CJ
Bevan
Mark D
MD
D000818:Animals; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D020864:Calcium Channels, N-Type / Q000502:physiology*; D018491:Dopamine Agonists / Q000494:pharmacology; D018492:Dopamine Antagonists / Q000494:pharmacology; D004307:Dose-Response Relationship, Radiation; D004347:Drug Interactions; D004558:Electric Stimulation / Q000379:methods; D005786:Gene Expression Regulation / Q000187:drug effects; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects; D009433:Neural Inhibition / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects; D009474:Neurons / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects; D018408:Patch-Clamp Techniques; D026902:Potassium Channel Blockers / Q000494:pharmacology; D019257:Quinpirole / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D017448:Receptors, Dopamine D2 / Q000502:physiology*; D051640:Small-Conductance Calcium-Activated Potassium Channels / Q000502:physiology*; D020531:Subthalamic Nucleus / Q000166:cytology*; D013469:Sulpiride / Q000494:pharmacology
C503279:Cacna1b protein, rat; D002121:Calcium Channel Blockers; D020864:Calcium Channels, N-Type; D018491:Dopamine Agonists; D018492:Dopamine Antagonists; D026902:Potassium Channel Blockers; D017448:Receptors, Dopamine D2; D051640:Small-Conductance Calcium-Activated Potassium Channels; D019257:Quinpirole; D013469:Sulpiride