Pharmacological characterization of a non-inactivating outward current observed in mouse cerebellar Purkinje neurones.
Whole-cell patch clamp recordings were used to investigate the properties of a non-inactivating outward current observed in mouse cerebellar Purkinje neurones at a holding potential of -20 mV. Increasing the external potassium (K(+)) concentration from 3 mM to 20 mM produced a rightward shift in the observed reversal potential of approximately 30 mV or approximately 40 mV for a K(+)-or a caesium (Cs(+))-based intracellular solution respectively, indicating the outward current was a K(+) current. The outward current was partially inhibited by the K(+) channel blocker, tetraethylammonium (TEA; IC(50)=0.15 mM). Subsequently, the background or TEA-insensitive current was measured in the presence of 1 mM TEA. The background current was reversibly inhibited by barium (Ba(2+); 300 microM, 50%) and potentiated by the application of arachidonic acid (AA; 1 mM, 62%). The volatile anaesthetic, halothane (1 mM), and the neuroprotectant, riluzole (500 microM), both reversibly inhibited the background current by 54% and 36% respectively. The background current was insensitive to changes in both intracellular and extracellular acidification. The GABA(B) and mu-opioid receptor agonists, baclofen and [D-Ala(2), N-MePhe(4)-Gly-ol(5)] enkephalin (DAMGO) both reversibly potentiated the outward current by 42% and 26% respectively. In contrast, the metabotropic glutamate receptor and acetylcholine receptor agonists, (S)-3,5-dihydroxyphenylglycine (DHPG) and muscarine both reversibly inhibited the outward current by 48% and 42% respectively. These data suggest that cerebellar Purkinje neurones possess a background current which shares several properties with recently cloned two-pore K(+) channels, particularly THIK-1.
Bushell
Trevor
T
Neuronal Excitability Group, Biochemistry Section, Department of Biological Sciences, Imperial College of Science, Technology and Medicine, London SW7 2BW. T.Bushell@ic.ac.uk
Clarke
Catherine
C
Mathie
Alistair
A
Robertson
Brian
B
D000818:Animals; D002531:Cerebellum / Q000166:cytology / Q000187:drug effects* / Q000502:physiology; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D051379:Mice; D026902:Potassium Channel Blockers / Q000494:pharmacology; D015221:Potassium Channels / Q000502:physiology*; D024683:Potassium Channels, Tandem Pore Domain; D011689:Purkinje Cells / Q000187:drug effects* / Q000502:physiology; D019789:Tetraethylammonium / Q000494:pharmacology
C486604:Kcnk13 protein, mouse; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D024683:Potassium Channels, Tandem Pore Domain; D019789:Tetraethylammonium