Downregulation of transient K+ channels in dendrites of hippocampal CA1 pyramidal neurons by activation of PKA and PKC.
We have reported recently a high density of transient A-type K+ channels located in the distal dendrites of CA1 hippocampal pyramidal neurons and shown that these channels shape EPSPs, limit the back-propagation of action potentials, and prevent dendritic action potential initiation (). Because of the importance of these channels in dendritic signal propagation, their modulation by protein kinases would be of significant interest. We investigated the effects of activators of cAMP-dependent protein kinase (PKA) and the Ca2+-dependent phospholipid-sensitive protein kinase (PKC) on K+ channels in cell-attached patches from the distal dendrites of hippocampal CA1 pyramidal neurons. Inclusion of the membrane-permeant PKA activators 8-bromo-cAMP (8-br-cAMP) or forskolin in the dendritic patch pipette resulted in a depolarizing shift in the activation curve for the transient channels of approximately 15 mV. Activation of PKC by either of two phorbol esters also resulted in a 15 mV depolarizing shift of the activation curve. Neither PKA nor PKC activation affected the sustained or slowly inactivating component of the total outward current. This downregulation of transient K+ channels in the distal dendrites may be responsible for some of the frequently reported increases in cell excitability found after PKA and PKC activation. In support of this hypothesis, we found that activation of either PKA or PKC significantly increased the amplitude of back-propagating action potentials in distal dendrites.
Hoffman
D A
DA
Division of Neuroscience, Baylor College of Medicine, Houston, Texas 77030, USA.
Johnston
D
D
D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine / Q000494:pharmacology; D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology; D000200:Action Potentials / Q000187:drug effects / Q000502:physiology; D000818:Animals; D002273:Carcinogens / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism*; D003712:Dendrites / Q000737:chemistry / Q000201:enzymology*; D003839:Deoxyadenosines / Q000494:pharmacology; D015536:Down-Regulation / Q000502:physiology; D004347:Drug Interactions; D004594:Electrophysiology; D004789:Enzyme Activation / Q000187:drug effects / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006624:Hippocampus / Q000166:cytology / Q000502:physiology; D009924:Organ Culture Techniques; D010703:Phorbol Esters / Q000494:pharmacology; D015221:Potassium Channels / Q000502:physiology*; D011493:Protein Kinase C / Q000378:metabolism*; D017966:Pyramidal Cells / Q000737:chemistry / Q000201:enzymology* / Q000648:ultrastructure; D051381:Rats; D017207:Rats, Sprague-Dawley
D002273:Carcinogens; D003839:Deoxyadenosines; D004791:Enzyme Inhibitors; D010703:Phorbol Esters; D015221:Potassium Channels; C064049:1,N(6)-propanodeoxyadenosine; D015124:8-Bromo Cyclic Adenosine Monophosphate; D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D011493:Protein Kinase C