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The Journal of Neuroscience, 2001, 21:RC175:1-6
RAPID COMMUNICATION
Somatic Colocalization of Rat SK1 and D class (Cav
1.2) L-type Calcium Channels in Rat CA1 Hippocampal Pyramidal
Neurons
Sarah E. H.
Bowden,
Stephanie
Fletcher,
David J.
Loane, and
Neil V.
Marrion
Department of Pharmacology and Medical Research Council Center for
Synaptic Plasticity, University of Bristol, Bristol, BS8 1TD, United
Kingdom
In hippocampal neurons, the firing of a train of action potentials
is terminated by generation of the slow afterhyperpolarization (AHP).
Recordings from hippocampal slices have shown that the slow AHP likely
results from the activation of small-conductance calcium-activated
potassium (SK) channels by calcium (Ca2+) entry
through L-type Ca2+ channels. However, the relative
localization of these two channel subtypes is not known. The cloning
and characterization of three subtypes of SK channel has suggested that
SK1 may underlie generation of the slow AHP. Using a novel antibody
directed against rat SK1 (rSK1), it has been determined that the
rSK1 channel is primarily in the soma of hippocampal CA1 neurons. In
conjunction with antibodies directed against C (Cav1.2) and
D (Cav1.3) class L-type Ca2+ channel
1 subunits, it was observed that rSK1 channels were selectively
colocalized with D class L-type channels. This colocalization supports
the functional coupling of L-type and SK channels previously observed
in cell-attached patches from hippocampal neurons. However, it appears
contrary to the slow rise and decay of the slow AHP. Induction of
delayed facilitation of L-type Ca2+ channels in
cell-attached patches from hippocampal neurons evoked delayed opening
of coupled SK channels. Generation of ensemble currents produced
waveforms identical to the ionic current underlying the slow AHP
(IsAHP). Therefore, these data
indicate that the slow AHP is somatic in origin, resulting from delayed
facilitation of D class L-type Ca2+ channels
colocalized with rSK1 channels.
Key words:
calcium-activated potassium channel; slow
afterhyperpolarization; SK channel; calcium channel; delayed
facilitation; hippocampus
Copyright © Society for Neuroscience 0270-6474//$05.00/0
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