ISSN:
1432-2013
Keywords:
Striatal neurons ATP-sensitive K+ channels
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Abstract. The characteristics of adenosine 5′-triphosphate (ATP)-sensitive K+ channels in acutely isolated striatal neurons from adult rats were examined. Neurons had a resting membrane potential of –53.9±1.2 mV (n=66), with evoked or spontaneous action potentials firing at 10±0.7 Hz, and large inwards and outwards whole-cell currents. In cell-attached patches with a high [K+] in the pipette, a voltage-independent, ATP-insensitive 16.5±1.5 pS channel was observed in 375 out of 452 cells. Bath application of Na+-azide (0.5–2 mM) to 108 neurons revealed another 145.7±3.5 pS (LKATP) channel in 65 neurons; this channel was blocked by tolbutamide. The LKATP channel exhibited a high open probability (P o, 0.8±0.05) at 0 mV pipette potential. Varying the pipette [K+] shifted the reversal potential of LKATP, showing the channel's K+ selectivity. Cytoplasmic ATP (ATPi) reversibly inhibited LKATP, with an inhibitory constant (K i) of 0.12 mM. LKATP was sensitive to intracellular Ca2+ but insensitive to iberiotoxin. In 25% of cell-attached patches, the presence of quinpirole in the pipette opened a third type of channel (90.6±1.7 pS, termed D2KATP). Sulpiride, a dopamine D2-receptor antagonist, inhibited D2KATP. ATPi reversibly inhibited D2KATP, with a K i of 0.212 mM. The Na+-azide- or quinpirole-induced current caused a tolbutamide-sensitive membrane hyperpolarization and a marked reduction in action potential frequency. We propose that ATP-sensitive K+ channels play a metabolism-dependent role in striatal neurons.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/s004240000322
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