2,2,2-Trichloroethanol Activates a Nonclassical Potassium Channel in Cerebrovascular Smooth Muscle and Dilates the Middle Cerebral Artery

Abstract

Trichloroacetaldehyde monohydrate [chloral hydrate (CH)] is a sedative/hypnotic that increases cerebral blood flow (CBF), and its active metabolite 2,2,2-trichloroethanol (TCE) is an agonist for the nonclassical two-pore domain K ϩ (K 2P ) channels TREK-1 and TRAAK. We sought to determine whether TCE dilates cerebral arteries in vitro by activating nonclassical K ϩ channels. TCE dilated pressurized and perfused rat middle cerebral arteries (MCAs) in a manner consistent with activation of nonclassical K ϩ channels. Dilation to TCE was inhibited by elevated external K ϩ but not by an inhibitory cocktail (IC) of classical K ϩ channel blockers. Patch-clamp electrophysiology revealed that, in the presence of the IC, TCE increased wholecell currents and hyperpolarized the membrane potential of isolated MCA smooth muscle cells. Heating increased TCEsensitive currents, indicating that the activated channel was thermosensitive. Immunofluorescence in sections of the rat MCA demonstrated that, like TREK-1, TRAAK is expressed in the smooth muscle of cerebral arteries. Isoflurane did not, however, dilate the MCA, suggesting that TREK-1 was not functional. These data indicate that TCE activated a nonclassical K ϩ channel with the characteristics of TRAAK in rat MCA smooth-muscle cells. Stimulation of K ϩ channels such as TRAAK in cerebral arteries may therefore explain in part how CH/TCE increases CBF.

Store-operated calcium entry is present in HL-1 cardiomyocytes and contributes to resting calcium

“…Micropipettes (3–5 MΩ resistance) were filled with pipette buffer (in mM: 140 CsCl, 1.0 MgCl 2 , 10 EGTA: ~6×10 −15 M free Ca 2+ , and 10 HEPES) with pH adjusted to 7.2 using CsOH). Whole-cell patch clamping was performed as described previously [21]. …”

Halogenated Ether, Alcohol, and Alkane Anesthetics Activate TASK-3 Tandem Pore Potassium Channels Likely through a Common Mechanism

“…TASK-3 activation studies have been limited to several clinical anesthetics: TASK-3 is activated by isoflurane, halothane, and chloroform; conversely, TASK-3 is unaffected by nonhalogenated nitrous oxide, cyclopropane, propofol, and xenon and is inhibited by local anesthetics (e.g., bupivicaine) (Kindler et al, 1999;Talley and Bayliss, 2002;Gruss et al, 2004;Andres-Enguix et al, 2007). TCE (2,2,2tricholoroethanol), an active metabolite of the hypnotic chloral hydrate, a GABA A chloride channel activator, activates TREK-1 and TRAAK tandem pore potassium channels (Krasowski et al, 1998;Krasowski and Harrison, 2000;Harinath and Sikdar, 2004;Parelkar et al, 2010). The effects of TCE on TASK-3 have not been reported.…”

Phosphatidylinositol 3,5-bisphosphate increases intracellular free Ca2+in arterial smooth muscle cells and elicits vasocontraction

“…The membrane potential of freshly dissociated aortic smooth muscle cells was determined by patch-clamp electrophysiology similar to a previous study by our laboratory (47). Briefly, aortas were enzymatically digested, and smooth muscle cells were isolated as described above.…”