Intermediate conductance calcium-activated potassium channels modulate summation of parallel fiber input in cerebellar Purkinje cells.
Encoding sensory input requires the expression of postsynaptic ion channels to transform key features of afferent input to an appropriate pattern of spike output. Although Ca(2+)-activated K(+) channels are known to control spike frequency in central neurons, Ca(2+)-activated K(+) channels of intermediate conductance (KCa3.1) are believed to be restricted to peripheral neurons. We now report that cerebellar Purkinje cells express KCa3.1 channels, as evidenced through single-cell RT-PCR, immunocytochemistry, pharmacology, and single-channel recordings. Furthermore, KCa3.1 channels coimmunoprecipitate and interact with low voltage-activated Cav3.2 Ca(2+) channels at the nanodomain level to support a previously undescribed transient voltage- and Ca(2+)-dependent current. As a result, subthreshold parallel fiber excitatory postsynaptic potentials (EPSPs) activate Cav3 Ca(2+) influx to trigger a KCa3.1-mediated regulation of the EPSP and subsequent after-hyperpolarization. The Cav3-KCa3.1 complex provides powerful control over temporal summation of EPSPs, effectively suppressing low frequencies of parallel fiber input. KCa3.1 channels thus contribute to a high-pass filter that allows Purkinje cells to respond preferentially to high-frequency parallel fiber bursts characteristic of sensory input.
Hotchkiss Brain Institute,  University of Calgary, Calgary, AB,  Canada T2N 4N1.
Jordan D T
JD
Engbers
Dustin
D
Anderson
Hadhimulya
H
Asmara
Renata
R
Rehak
W Hamish
WH
Mehaffey
Shahid
S
Hameed
Bruce E
BE
McKay
Mirna
M
Kruskic
Gerald W
GW
Zamponi
Ray W
RW
Turner
D000818:Animals; D005260:Female; D007150:Immunohistochemistry; D051660:Intermediate-Conductance Calcium-Activated Potassium Channels / Q000502:physiology*; D011247:Pregnancy; D011689:Purkinje Cells / Q000378:metabolism / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley
D051660:Intermediate-Conductance Calcium-Activated Potassium Channels