Abstract
T-type calcium channels have been implicated in many behaviorally important neurophysiological processes, and altered channel activity has been linked to the pathophysiology of neurological disorders such as insomnia, epilepsy, Parkinson's disease, depression, schizophrenia, and pain. We have previously identified a number of potent and selective T-type channel antagonists (Barrow et al., 2007; Shipe et al., 2008; Yang et al., 2008). Here we describe the properties of the antagonist TTA-A2 [2-(4-cyclopropylphenyl)-N-((1R)-1-{5-[(2,2,2-trifluoroethyl)oxo]-pyridin-2-yl}ethyl)acetamide], assessed in patch-clamp experiments. TTA-A2 blocks T-type channels (Cav3.1, 3.2, 3.3) voltage dependently and with high potency (IC50 ∼100 nM). Stimulation at 3 Hz revealed additional use dependence of inhibition. A hyperpolarized shift of the channel availability curve and delayed channel recovery from inactivation suggest that the compound preferentially interacts with and stabilizes inactivated channels. The compound showed a ∼300-fold selectivity for Cav3 channels over high-voltage activated calcium channels. Inhibitory effects on native T-type currents were confirmed in brain slice recordings from the dorsal lateral geniculate nucleus and the subthalamic nucleus. Furthermore, we demonstrate that in vivo T-type channel inhibition by TTA-A2 suppresses active wake and promotes slow-wave sleep in wild-type mice but not in mice lacking both Cav3.1 and Cav3.3, suggesting the selective effect of TTA-A2 on recurrent thalamocortical network activity. The discovery of the potent and selective T-type channel antagonist TTA-A2 has enabled us to study the in vivo effects of pharmacological T-channel inhibition on arousal in mice, and it will help to explore the validity of these channels as potential drug targets for sleep-related and other neurological diseases.
Footnotes
-
Article, publication date, and citation information can be found at http://jpet.aspetjournals.org.
doi:10.1124/jpet.110.171058.
-
ABBREVIATIONS:
- TTA-A2
- 2-(4-cyclopropylphenyl)-N-((1R)-1-{5-[(2,2,2-trifluoroethyl)oxo]-pyridin-2-yl}ethyl)acetamide
- LTS
- low-threshold spikes
- EEG
- electroencephalogram
- EMG
- electromyogram
- ECoG
- electrocorticogram
- REM
- rapid eye movement
- dLGN
- dorsal lateral geniculate nucleus
- STN
- subthalamic nucleus
- DMSO
- dimethyl sulfoxide
- CRS
- choline replacement solution
- aCSF
- artificial cerebrospinal fluid
- HEK
- human embryonic kidney
- CI
- confidence interval.
- Received June 4, 2010.
- Accepted August 3, 2010.
- Copyright © 2010 by The American Society for Pharmacology and Experimental Therapeutics
JPET articles become freely available 12 months after publication, and remain freely available for 5 years.Non-open access articles that fall outside this five year window are available only to institutional subscribers and current ASPET members, or through the article purchase feature at the bottom of the page.
|