Although it is well established that low-voltage-activated T-type Ca(2+) channels play a key role in many neurophysiological functions and pathological states, the lack of selective and potent antagonists has so far hampered a detailed analysis of the full impact these channels might have on single-cell and neuronal network excitability as well as on Ca(2+) homeostasis. Recently, a novel series of piperidine-based molecules has been shown to selectively block recombinant T-type but not high-voltage-activated (HVA) Ca(2+) channels and to affect a number of physiological and pathological T-type channel-dependent behaviors. Here we directly show that one of these compounds, 3,5-dichloro-N-[1-(2,2-dimethyl-tetrahydro-pyran-4-ylmethyl)-4-fluoro-piperidin-4-ylmethyl]-benzamide (TTA-P2), exerts a specific, potent (IC(50) = 22 nm), and reversible inhibition of T-type Ca(2+) currents of thalamocortical and reticular thalamic neurons, without any action on HVA Ca(2+) currents, Na(+) currents, action potentials, and glutamatergic and GABAergic synaptic currents. Thus, under current-clamp conditions, the low-threshold Ca(2+) potential (LTCP)-dependent high-frequency burst firing of thalamic neurons is abolished by TTA-P2, whereas tonic firing remains unaltered. Using TTA-P2, we provide the first direct demonstration of the presence of a window component of Ca(2+) channels in neurons and its contribution to the resting membrane potential of thalamic neurons and to the Up state of their intrinsically generated slow (<1 Hz) oscillation. Moreover, we demonstrate that activation of only a small fraction of the T-type channel population is required to generate robust LTCPs, suggesting that LTCP-driven bursts of action potentials can be evoked at depolarized potentials where the vast majority of T-type channels are inactivated.

https://www.jneurosci.org/content/jneuro/30/1/99.full.pdf

Selective T-Type Calcium Channel Block in Thalamic Neurons Reveals Channel Redundancy and Physiological Impact of ITwindow

Slow waves represent one of the prominent EEG signatures of non-rapid eye movement (non-REM) sleep and are thought to play an important role in the cellular and network plasticity that occurs during this behavioral state. These slow waves of natural sleep are currently considered to be exclusively generated by intrinsic and synaptic mechanisms within neocortical territories, although a role for the thalamus in this key physiological rhythm has been suggested but never demonstrated. Combining neuronal ensemble recordings, microdialysis, and optogenetics, here we show that the block of the thalamic output to the neocortex markedly (up to 50%) decreases the frequency of slow waves recorded during non-REM sleep in freely moving, naturally sleeping-waking rats. A smaller volume of thalamic inactivation than during sleep is required for observing similar effects on EEG slow waves recorded during anesthesia, a condition in which both bursts and single action potentials of thalamocortical neurons are almost exclusively dependent on T-type calcium channels. Thalamic inactivation more strongly reduces spindles than slow waves during both anesthesia and natural sleep. Moreover, selective excitation of thalamocortical neurons strongly entrains EEG slow waves in a narrow frequency band (0.75–1.5 Hz) only when thalamic T-type calcium channels are functionally active. These results demonstrate that the thalamus finely tunes the frequency of slow waves during non-REM sleep and anesthesia, and thus provide the first conclusive evidence that a dynamic interplay of the neocortical and thalamic oscillators of slow waves is required for the full expression of this key physiological EEG rhythm.

https://www.jneurosci.org/content/jneuro/33/50/19599.full.pdf

Essential Thalamic Contribution to Slow Waves of Natural Sleep

It is well recognized that voltage-gated calcium (Ca2+) channels modulate the function of peripheral and central pain pathways by influencing fast synaptic transmission and neuronal excitability. In the past, attention focused on the modulation of different subtypes of high-voltage-activated-type Ca2+ channels; more recently, the function of low-voltage-activated or transient (T)-type Ca2+ channels (T-channels) in nociception has been well documented. Currently, available pain therapies remain insufficient for certain forms of pain associated with chronic disorders (e.g. neuropathic pain) and often have serious side effects. Hence, the identification of selective and potent inhibitors and modulators of neuronal T-channels may help greatly in the development of safer, more effective pain therapies. Here, we summarize the available information implicating peripheral and central T-channels in nociception. We also discuss possible future developments aimed at selective modulation of function of these channels, which are highly expressed in nociceptors.

https://bpspubs.onlinelibrary.wiley.com/doi/pdf/10.1111/j.1476-5381.2011.01256.x

T-type voltage-gated calcium channels as targets for the development of novel pain therapies

Several agents that are preferential T-type calcium (T-channel) blockers have shown promise as being effective in alleviating acute and chronic pain, suggesting an urgent need to identify even more selective and potent T-channel antagonists We used small, acutely dissociated dorsal root ganglion (DRG) cells of adult rats to study the in vitro effects of 3,5-dichloro-N-[1-(2,2-dimethyl-tetrahydro-pyran-4-ylmethyl)-4-fluoro-piperidin-4-ylmethyl]-benzamide (TTA-P2), a derivative of 4-aminomethyl-4-fluoropiperdine, on T currents, as well as other currents known to modulate pain transmission We found that TTA-P2 potently and reversibly blocked DRG T currents with an IC(50) of 100 nM and stabilized channel in the inactive state, whereas high-voltage-activated calcium and sodium currents were 100- to 1000-fold less sensitive to channel blocking effects In in vivo studies, we found that intraperitoneal injections of 5 or 75 mg/kg TTA-P2 reduced pain responses in mice in phases 1 and 2 of the formalin test Furthermore, TTA-P2, at 10 mg/kg ip, selectively and completely reversed thermal hyperalgesia in diabetic rats treated with streptozocin but had no effect on the nociceptive response of healthy animals The antihyperalgesic effects of TTA-P2 in diabetic rats were completely abolished by administration of oligonucleotide antisense for Ca(V)32 isoform of T channels Thus, TTA-P2 is not only the most potent and selective blocker of T channels in sensory neurons yet described, but it also demonstrates the potential for the pharmacological effectiveness of this approach in addressing altered nociceptive responses in animal models of both inflammatory and neuropathic pain

/pdf/tta-p2-is-a-potent-and-selective-blocker-of-t-type-calcium-3zu21o3n1m.pdf

TTA-P2 is a potent and selective blocker of T-type calcium channels in rat sensory neurons and a novel antinociceptive agent.

The Hyperpolarization-activated Cyclic Nucleotide-gated (HCN) channels are subthreshold, voltage-gated ion channels that are highly expressed in hippocampal and cortical pyramidal cell dendrites, where they play an important role in regulating synaptic potential integration and plasticity. Here, we demonstrate that HCN1 subunits are also localized to the active zone of mature asymmetric synaptic terminals targeting mouse entorhinal cortical layer III pyramidal neurons. We found that HCN channels inhibit glutamate synaptic release by suppressing the activity of low threshold voltage-gated T- (CaV3.2) type Ca2+ channels. In agreement, electron microscopy showed the co-localisation of pre-synaptic HCN1 and CaV3.2 subunit. This represents a novel mechanism by which HCN channels regulate synaptic strength and thereby neural information processing and network excitability.

/pdf/presynaptic-hcn1-channels-regulate-cav3-2-activity-and-2vswlct9if.pdf

Presynaptic HCN1 channels regulate Cav3.2 activity and neurotransmission at select cortical synapses.

The novel T-type antagonist (S)-5 has been prepared and evaluated in in vitro and in vivo assays for T-type calcium ion channel activity. Structural modification of the piperidine leads 1 and 2 afforded the fluorinated piperidine (S)-5, a potent and selective antagonist that displayed in vivo CNS efficacy without adverse cardiovascular effects.

Design, synthesis, and evaluation of a novel 4-aminomethyl-4-fluoropiperidine as a T-type Ca2+ channel antagonist.

Discovery and expanded SAR of 4,4-disubstituted quinazolin-2-ones as potent T-type calcium channel antagonists.

The present invention is directed to quinoline amide compounds of formula (I) which are M1 receptor positive allosteric modulators and that are useful in the treatment of diseases in which the M1 receptor is involved, such as Alzheimer's disease, schizophrenia, pain or sleep disorders. The invention is also directed to pharmaceutical compositions comprising the compounds, and to the use of the compounds and compositions in the treatment of diseases mediated by the M1 receptor.

Quinoline amide m1 receptor positive allosteric modulators

The present invention is directed to quinoline amide compounds of formula (I)wherein all the substituents are disclosed in the claims, which are M1 receptor positive allosteric modulators and can be useful in the treatment of diseases in which the M1 receptor is involved, such as Alzheimer's disease, schizophrenia, pain or sleep disorders. The invention is also directed to pharmaceutical compositions comprising the compounds, and to the use of the compounds and compositions in the treatment of diseases mediated by the M1 receptor.

Schlegel Kelly-Ann

Papers

Design, synthesis, and evaluation of a novel 4-aminomethyl-4-fluoropiperidine as a T-type Ca2+ channel antagonist.

Discovery and expanded SAR of 4,4-disubstituted quinazolin-2-ones as potent T-type calcium channel antagonists.

Quinoline amide m1 receptor positive allosteric modulators

Quinoline amide compounds which are muscarinic m1 receptor positive allosteric modulators