Calcium Channel Currents Research Articles

Inhibition Effect of IL-1β on Calcium Channels Currents in Cultured Cortical Neurons of Rat

Interleukin-1beta (IL-1beta) is an important proinflammatory cytokine that exert wide biological functions in the central nervous system (CNS). Voltage-gated Ca2+ channels in plasma membrane are essential components of Ca2+ signal whose change on pathological conditions is closely related to processes of diseases. Although both IL-1beta and Ca2+ channels have key roles in injury and disease of the brain, so far their relations have been reported in few studies. The effects of IL-1beta on Ca2+ channels in cultured cortical neurons of rats were investigated using patch-clamp recording in present research. Our results showed that both 10 and 50 ng/mL of IL-1beta treatment inhibit the Ca2+ currents in time and dose dependent manner, without the change of activation properties of voltage-gated Ca2+ channels (VGCC)s.

Inhibition Effect of IL-1β on Calcium Channels Currents in Cultured Cortical Neurons of Rat

Interleukin-1β(IL-1β) is an important porinflammatory cytokine that exert wide biological functions in the central nervous system (CNS). Voltage-gated Ca²⁺ channels in plasma membrane are essential components of Ca²⁺ signal whose change on pathological conditions is closely related to processes of diseases. Although both IL-1βand Ca²⁺ channels have key roles in injury and disease of the brain, so far their relations have been reported in few studies. The effects of IL-1βon Ca²⁺ channels in cultured cortical neurons of rats were investigated using patch-clamp recording in present research. Our results showed that both 10 and 50 ng/mL of IL-1βtreatment inhibit the Ca²⁺ currents in time and dose dependent manner, without the change of activation properties of voltage-gated Ca²⁺ channels (VGCC)s.

Inhibition of L-type calcium currents by salusin-β in rat cardiac ventricular myocytes

Salusin -β is a new regulatory peptide relevant to the cardiovascular system and exerts negative inotropic effect on ventricular muscle. The purpose of the present study was to determine whether salusin-β can inhibit cardiac L-type calcium channel current ( I Ca,L). Using whole-cell voltage-clamp techniques, I Ca,L was measured in ventricular myocytes isolated from 12 to 16 weeks rats. Salusin-β dose-dependently and reversibly reduced the magnitude of I Ca,L in rat ventricular myocytes. Neither threshold potential nor the peak potential of current–voltage relationship was affected. Salusin-β increased the rate of I Ca,L inactivation without altering its gating properties. These results suggest salusin-β inhibited I Ca,L by increasing the rate of I Ca,L inactivation and the inhibition of L-type Ca 2+ channels induced by salusin-β may contribute to its negative inotropic effect on ventricular muscle.

(R)-roscovitine prolongs the mean open time of unitary N-type calcium channel currents

(R)-roscovitine (Ros) is a cyclin-dependent kinase inhibitor that also has been shown to have direct agonist and antagonist actions on Ca v2.1 (P/Q-type) and Ca v 2.2 (N-type) families of voltage-gated calcium channels. These kinase-independent effects represent a novel opportunity to advance our understanding of calcium channel function and calcium-triggered neurotransmitter release. Furthermore, such actions on calcium channels may direct the development of Ros derivatives as new therapeutic agents. We used patch clamp recordings to characterize mechanisms that underlie the agonist effects of Ros on unitary N-type calcium channel gating. We found that N-type channels normally gate with either a short or long mean open time, that Ros significantly prolonged the mean open time of the long gating component and increased the probability of observing channels that gated with a long open time, but had no effect on single channel conductance. Using Monte Carlo simulations of a single channel kinetic model and Ros interactions, we were able to reproduce our experimental results and investigate the model's microscopic dynamics. In particular, our simulations predicted that the longer open times generated by Ros were due to the appearance of a long open state combined with an increased amount of time spent in transitions between open states. Our results suggest a mechanism for agonist effects of Ros at the level of single channels, and provide a mechanistic explanation for previously reported agonist effects on whole cell calcium currents.

Decreased calcium channel currents and facilitated epinephrine release in the Ca 2+ channel β3 subunit-null mice

The β subunits of voltage-dependent calcium channels are known to modify calcium channel currents through pore-forming α1 subunits. The β3 subunit is expressed in the adrenal gland and participates in forming various calcium channel types. We performed a series of experiments in β3-null mice to determine the role of the β3 subunit in catecholamine release from the adrenal chromaffin system. Protein levels of N-type channel forming CaV2.2 and L-type forming CaV1.2 decreased. The β3-null mice showed a decreased baroreflex, suggesting decreased sympathetic tonus, whereas plasma catecholamine levels did not change. Pulse-voltage stimulation revealed significantly increased amperometrical currents in β3-null mice, while patch–clamp recordings showed a significant reduction in Ca 2+-currents due to reduced L- and N-type currents, indicating facilitated exocytosis. A biochemical analysis revealed increased InsP3 production. In conclusion, our results indicate the importance of the β3 subunit in determining calcium channel characteristics and catecholamine release in adrenal chromaffin cells.

Lysophospholipids Modulate Voltage-Gated Calcium Channel Currents in Pituitary Cells; Effects of Lipid-Stress

Voltage-gated calcium channels (VGCCs) are osmosensitive. The hypothesis that this property of VGCCs stems from their susceptibility to alterations in the mechanical properties of the bilayer was tested on VGCCs in pituitary cells using cone-shaped lysophospholipids (LPLs) to perturb bilayer lipid stress. LPLs of different head group size and charge were used: lysophosphatidylcholine (LPC), lysophosphatidylinositol (LPI), lysophosphatidylserine (LPS) and lysophosphatidylethanolamine (LPE). Phosphatidylcholine (PC) and LPC (C6:0) were used as controls. We show that partition of both LPC and LPI into the membrane of pituitary cells suppressed L-type calcium channel currents (I(L)). This suppression of I(L) was slow in onset, reversible upon washout with BSA and associated with a depolarizing shift in activation ( approximately 8mV). In contrast to these effects of LPC and LPI on I(L), LPS, LPE, PC and LPC (C6:0) exerted minimal or insignificant effects. This difference may be attributed to the prominent conical shape of LPC and LPI compared to the shapes of LPS and LPE (which have smaller headgroups), and to PC (which is cylindrical). The similar effects of LPC and LPI on I(L), despite differences in the structure and charge of their headgroups suggest a common lipid stress dependent mechanism in their action on VGCCs.

α5β1 Integrin Engagement Increases Large Conductance, Ca2+-activated K+ Channel Current and Ca2+ Sensitivity through c-src-mediated Channel Phosphorylation

Large conductance, calcium-activated K(+) (BK) channels are important regulators of cell excitability and recognized targets of intracellular kinases. BK channel modulation by tyrosine kinases, including focal adhesion kinase and c-src, suggests their potential involvement in integrin signaling. Recently, we found that fibronectin, an endogenous alpha5beta1 integrin ligand, enhances BK channel current through both Ca(2+)- and phosphorylation-dependent mechanisms in vascular smooth muscle. Here, we show that macroscopic currents from HEK 293 cells expressing murine BK channel alpha-subunits (mSlo) are acutely potentiated following alpha5beta1 integrin activation. The effect occurs in a Ca(2+)-dependent manner, 1-3 min after integrin engagement. After integrin activation, normalized conductance-voltage relations for mSlo are left-shifted at free Ca(2+) concentrations >or=1 microm. Overexpression of human c-src with mSlo, in the absence of integrin activation, leads to similar shifts in mSlo Ca(2+) sensitivity, whereas overexpression of catalytically inactive c-src blocks integrin-induced potentiation. However, neither integrin activation nor c-src overexpression potentiates current in BK channels containing a point mutation at Tyr-766. Biochemical tests confirmed the critical importance of residue Tyr-766 in integrin-induced channel phosphorylation. Thus, BK channel activity is enhanced by alpha5beta1 integrin activation, likely through an intracellular signaling pathway involving c-src phosphorylation of the channel alpha-subunit at Tyr-766. The net result is increased current amplitude, enhanced Ca(2+) sensitivity, and rate of activation of the BK channel, which would collectively promote smooth muscle hyperpolarization in response to integrin-extracellular matrix interactions.

Analgesic α-conotoxins Vc1.1 and Rg1A inhibit N-type calcium channels in sensory neurons of α9 nicotinic receptor knockout mice

α-Conotoxins Vc1.1 and Rg1A are peptides from the venom of marine Conus snails that are currently in development as a treatment for neuropathic pain. We have reported previously that the α9α10 nicotinic acetylcholine receptor (nAChR) selective-conotoxins Vc1.1 and Rg1A potently and selectively inhibit high voltage-activated (HVA) N-type calcium channel currents in dissociated neurons from rat dorsal root ganglia (DRG). Our data indicated that Vc1.1 does not interact directly with N-type Ca2+ channels but inhibits them via GABAB receptor activation. The present study investigated Vc1.1 and Rg1A inhibition of N-type Ca2+ channels currents in DRG neurons of wild-type and α9 knockout (KO) mice to determine if the α9 nAChR was necessary for inhibition of the Ca2+ channel current. Application of Vc1.1 (100 nM) inhibited N-type Ca2+ channel currents to 69.2 ± 3.5% of control in DRG neurons isolated from wild-type mice. In {greater than or equal to >70% of DRG neurons isolated from the α9 KO mice, both Vc1.1 and Rg1A selectively inhibited N-type Ca2+ channel currents with an IC50 of 24.6 nM and 22.4 nM, respectively. The GABAB receptor antagonist CGP55845 (1 μM) antagonized the effect of Vc1.1 and Rg1A on the N-type Ca2+ channels in α9 KO mice. RT-PCR and western blot analysis confirmed the absence of the α9 nAChR in mice carrying a null mutation for the nAChR α9 gene. These results demonstrate that the inhibition of N-type Ca2+ channel channels by Vc1.1 and Rg1A is not mediated by the expression of α9α10 nAChRs in DRG neurons.

Calcium Currents in Chronically Dysfunctional Pig Myocardium

Chronic reduction in coronary artery blood flow due to stenosis results in reduced myocardial contractile function, termed “hibernating” myocardium. This change involves electrical remodeling and a propensity for sudden cardiac death in the absence of infarction. We used a pig model of chronic left anterior descending artery stenosis to study calcium currents associated with the hibernating myocardium. We developed a cell isolation technique from punch biopsies of the left ventricle. This yields calcium-tolerant isolated myocytes with brick shaped morphology and clear striation patterns. Myocyte length from hibernating myocardium averaged 145 ± 7.7 (n=15) vs. 124 ± 4.8 μm (n=42) for control, suggesting cellular hypertrophy. The cell shortening of hibernating cells was also reduced compared to the remote region from 6.4 ± 1% (n=21) to 4.45 ± 1% (n=11) suggesting that the reduced contractility seen in the hibernating region was preserved in the isolated myocytes. Furthermore, cells isolated from hibernating myocardium had significantly higher numbers of premature contractions 4/15 for hibernating vs. 0/19 for control suggesting a cellular propensity for arrhythmias. The L-type calcium channel current (ICa,L) in myocytes from hibernating myocardium (1.35 ± 0.08 pA/pF, n=22) was reduced compared to normal myocardium (1.96 ± 0.07 pA/pF, n=33; P<0.01). The voltage dependence of steady state activation and inactivation were nearly identical. Isoproterenol (100 nM) shifted the activation curves nearly identically for both groups, but the ability of isoproterenol to enhance the current was decreased from a 4.1 ± 0.48 fold increase to a 2.64 ± 0.37 (p < 0.05). Finally, the recovery rate for calcium current was reduced by hibernation, reflecting an approximate 20 mV shift. These changes in L-type calcium current and isoproterenol response may explain the reduced contractility of hibernating myocytes and the increased the likelihood of sudden cardiac arrhythmias.

Polyhistidine Peptide Inhibitor of the Aβ Calcium Channel Potently Blocks the Aβ-Induced Calcium Response in Cells

Based on the consistent demonstrations that the Aβ peptide of Alzheimer's disease forms calcium permeant channels in artificial membranes, we have proposed that the intracellular calcium increase observed in cells exposed to Aβ is initiated by calcium fluxes through Aβ channels. We have found that a small four histidine peptide, NAHis04, potently inhibits the Aβ-induced calcium channel currents in artificial lipids membrane. Here we report that NaHis04 also potently blocks the intracellular calcium increase which is observed in cells exposed to Aβ.

Sensitization of voltage activated calcium channel currents for capsaicin in nociceptive neurons by tumor-necrosis-factor-α

It is known that application of tumor-necrosis-factor-α (TNF-α) sensitizes neuronal calcium channels for heat stimuli in rat models of neuropathic pain. This study examines whether TNF-α modulates the capsaicin-induced effects after transient receptor potential vanilloid (TRPV)-1 receptor activation on voltage activated calcium channel currents ( I Ca(V)). TRPV-1 receptors are activated by heat and play an important role in the pathogenesis of thermal hyperalgesia in neuropathic pain syndromes, while voltage activated channels are essential for transmission of neuronal signals. Eliciting I Ca(V) in DRG neurons of rats by a depolarization from the resting potential to 0 mV, TNF-α (100 ng/ml) reduces I Ca(V) by 16.9 ± 2.2%, while capsaicin (0.1 μM) decreases currents by 27 ± 4.3%. Pre-application of TNF-α (100 ng/ml) for 24 h results in a sensitization of I Ca(V) to capsaicin (0.1 μM) with a reduction of 42.8 ± 4.4% mediated by TRPV-1. While L-type (36.6 ± 5.2%) and P/Q-type currents (35.6 ± 4.1%) are also sensitized by TRPV-1 activation, N-type channel currents are most sensitive (74.5 ± 7.3%). The capsaicin-induced shift towards the hyperpolarizing voltage range does not occur when TNF-α is applied. Summarizing, TNF-α sensitizes nociceptive neurons for capsaicin.

Hydrogen Sulfide’s Involvement in Modulating Nociception

Hydrogen sulfide (H2S) is a malodorous gas which functions as an endogenous gasotransmitter in humans. It is becoming appreciated that H2S may be involved in a wide variety of processes including nociceptive processes. The molecular mechanisms responsible for many of the activities of H2S remain uncertain, however, H2S increases cAMP levels in neuronal and glial cell lines and primary neuron cultures with hyperpolarization. H2S may be involved in multiple signaling pathways and produce various effects on ion channels (e.g. T-type calcium channel currents, ATP-sensitive K+ (KATP) channels) which may inhibit or promote nociception. It is also conceivable that H2S may affect the n-methyl-d aspartate (NMDA) receptor complex and/or TRPA1 ion channels which may modulate nociceptive processes. It appears that H2S may regulate key neuronal functions, including the induction of hippocampal long-term potentiation, a synaptic model of learning and memory thought to involve the NMDA receptor as well as the release of corticotrophin-releasing hormone from the hypothalamus. It seems that the primary role of H2S in nociceptive processes is the activation of T-type calcium channels leading to facilitation of pronociceptive processes. A secondary contribution to the facilitation of pronociceptive processes may come from H2S-induced activation. It would appear that much like other gasotransmitters (e.g. nitric oxide), endogenous H2S may be involved in multiple physiologic processes and its effects remain complex, difficult to predict, and may vary depending on the specific environment/circumstances/location where it is generated. A greater understanding of the clinically significant human physiology of H2S and hydrogen sulfide's effects on modulating nociceptive processes may potentially lead to novel targets for improving analgesia.

Effects of ShenSongYangXin on action potential and some current channels in isolated rabbit pulmonary vein cardiomyocytes

To investigate the effects of ShenSongYangXin on action potential and some current channels in isolated rabbit pulmonary vein cardiomyocytes and to elucidate its possible mechanism of curing atrial fibrillation. Action potentials as well as L-type calcium channel current (I(Ca-L)), transient outward potassium current (I(K1)) and inward rectifier potassium current (I(To)) were recorded using whole cell patch-clamp technique. ShenSongYangXin prolonged the action potential duration (APD) significantly, APD90 was enlarged from (187 +/- 49) ms to (286 +/- 76) ms at the concentration of 5 mg/ml and to (312 +/- 82) ms at the concentration of 10 mg/dl respectively (P < 0.05). It also depressed the current of I(Ca-L), I(K1) and Iro in a concentration-dependent manner. ShenSongYangXin can be used to treat atrial fibrillation through its actions on multiple current channels.

Augmented potassium current is a shared phenotype for two genetic defects associated with familial atrial fibrillation

Mutations in multiple genes have been implicated in familial atrial fibrillation (AF), but the underlying mechanisms, and thus implications for therapy, remain ill-defined. Among 231 participants in the Vanderbilt AF Registry, we found a mutation in KCNQ1 (encoding the α-subunit of slow delayed rectifier potassium current [ I Ks]) and separately a mutation in natriuretic peptide precursor A ( NPPA) gene (encoding atrial natriuretic peptide, ANP), both segregating with early onset lone AF in different kindreds. The functional effects of these mutations yielded strikingly similar I Ks “gain-of-function.” In Chinese Hamster Ovary (CHO) cells, coexpression of mutant KCNQ1 with its ancillary subunit KCNE1 generated ∼ 3-fold larger currents that activated much faster than wild-type (WT)- I Ks. Application of the WT NPPA peptide fragment produced similar changes in WT- I Ks, and these were exaggerated with the mutant NPPA S64R peptide fragment. Anantin, a competitive ANP receptor antagonist, completely inhibited the changes in I Ks gating observed with NPPA S64R. Computational simulations identified accelerated transitions into open states as the mechanism for variant I Ks gating. Incorporating these I Ks changes into computed human atrial action potentials (AP) resulted in 37% shortening (120 vs. 192 ms at 300 ms cycle length), reflecting loss of the phase II dome which is dependent on L-type calcium channel current. We found striking functional similarities due to mutations in KCNQ1 and NPPA genes which led to I Ks “gain-of-function”, atrial AP shortening, and consequently altered calcium current as a common mechanism between diverse familial AF syndromes.

Estradiol Reverses a Calcium-Related Biomarker of Brain Aging in Female Rats

An increase in L-type voltage-gated calcium channel (LTCC) current is a prominent biomarker of brain aging and is believed to contribute to cognitive decline and vulnerability to neuropathologies. Studies examining age-related changes in LTCCs have focused primarily on males, although estrogen (17beta-estradiol, E2) affects calcium-dependent activities associated with cognition. Therefore, to better understand brain aging in females, the effects of chronic E2 replacement on LTCC current activity in hippocampal neurons of young and aged ovariectomized rats were determined. The zipper slice preparation was used to expose cornu ammonis 1 (CA1) pyramidal neurons for recording LTCC currents using the cell-attached patch-clamp technique. We found that an age-related increase in LTCC current in neurons from control animals was prevented by E2 treatment. In addition, in situ hybridization revealed that within stratum pyramidale of the CA1 area, mRNA expression of the Ca(v)1.2 LTCC subunit, but not the Ca(v)1.3 subunit, was decreased in aged E2-treated rats. Thus, the reported benefits of E2 on cognition and neuronal health may be attributed, at least in part, to its age-related decrease in LTCC current.

Reactive oxygen species modulate neuronal excitability in rat intrinsic cardiac ganglia

Reactive oxygen species (ROS) are produced as by-products of oxidative metabolism and occur in the heart during ischemia and coronary artery reperfusion. The effects of ROS on the electrophysiological properties of intracardiac neurons were investigated in the intracardiac ganglion (ICG) plexus in situ and in dissociated neurons from neonatal and adult rat hearts using the whole-cell patch clamp recording configuration. Bath application of ROS donors, hydrogen peroxide (H2O2) and tert-butyl hydroperoxide (t-BHP) hyperpolarized, and increased the action potential duration of both neonatal and adult ICG neurons. This action was also recorded in ICG neurons in an adult in situ ganglion preparation. H2O2 and t-BHP also inhibited voltage-gated calcium channel (VGCC) currents and shifted the current–voltage (I–V) relationship to more hyperpolarized potentials. In contrast, H2O2 increased the amplitude of the delayed rectifier K+ current in neonatal ICG neurons. In neonatal ICG neurons, bath application of either superoxide dismutase (SOD) or catalase, scavengers of ROS, prior to H2O2 attenuated the hyperpolarizing shift but not the inhibition of VGCC by H2O2. In contrast, in adult ICG neurons, application of SOD alone had no effect upon either VGCC current amplitude or the I–V relationship, whereas application of SOD prior to H2O2 exposure abolished both the H2O2-mediated hyperpolarizing shift and inhibition. These data indicate that ROS alter depolarization-activated Ca2+ and K+ conductances which underlie neuronal excitability of ICG neurons. This affects action potential duration and therefore probably modifies autonomic control of the heart during ischemia/reperfusion.

Loss of Intracellular and Intercellular Synchrony of Calcium Release in Systolic Heart Failure

Normal contraction of cardiac muscle requires a coordinated cellular mechanical response to the electric pacemaker signal that begins in the sinoatrial node and spreads through the conduction system and ultimately across the ventricular myocardium via gap junctions. In ventricular myocytes, depolarization by the action potential causes clusters of L-type calcium channels (LCCs) to open, allowing a small amount of Ca to enter the diadic cleft space between the sarcolemma and the sarcoplasmic reticulum (SR). When the Ca concentration in this space becomes sufficiently high to gate ryanodine receptors (RyRs), they open and release SR Ca into the cytoplasm, so that it can bind to and activate myofilaments, resulting in force development. Each cluster of LCCs on the sarcolemma, its opposing cluster of RyRs across the 10- to 12-nm diameter diadic cleft space, and associated SR regulatory proteins is a couplon.1 According to the local control theory of cardiac excitation-contraction (EC) coupling, couplons are activated independently. Independent activation of couplons depends on the extent of LCC activation, providing a mechanism for regulation of contractile force by stochastic recruitment of couplons.2 In systolic heart failure, numerous cellular defects in EC coupling and Ca regulation have been identified that contribute to contractile dysfunction (and ventricular arrhythmias), although there is a host of other major abnormalities leading to loss of force development, including fibrosis,3 defective energy metabolism,4 pH changes,5 heterogeneous conductance across connexin hemichannels,6 and defects in sarcomeric proteins.7 Thus, it is important to keep in mind that no single defect can explain the contractile dysfunction of systolic failure. Article see p 223 Recent studies of defective EC coupling in heart failure have addressed not only reductions in the extent and kinetics of Ca released in response to the action potential (ie, reduced recruitment of couplons and …

Ginsenoside Rg1 Modulates Spontaneous Synchronous Ca2+ Oscillations of Cultured Hippocampal Neurons

Ginsenoside Rg1, the main active ingredient of Ginseng Radix which is a famous Chinese medicine, is widely used as an anti-stress, anti-aging and neurological performance improving agent. In this study, we used calcium imaging and whole-cell patch clamp techniques to investigate the effect of Ginsenoside Rg1 on spontaneous and synchronous Ca 2+ oscillations and the possible mechanisms in primarily cultured hippocampal neuronal networks. We found that Ginse- noside Rg1 could decrease the frequencies of spontaneous and synchronous Ca 2+ oscillations and inhibit the amplitude of high-voltage activated calcium channel currents. These results provided the experimental evidence for the clinical applica- tion of Rg1 as a neuroprotector on the cellular level, and enriched the theoretical system of Chinese medicine.

Protein Kinase A Activity Controls the Regulation of T-type CaV3.2 Channels by Gβγ Dimers

Low voltage-activated (LVA), T-type, calcium channels mediate diverse biological functions and are inhibited by Gbetagamma dimers, yet the molecular events required for channel inhibition remain unknown. Here, we identify protein kinase A (PKA) as a molecular switch that allows Gbeta(2)gammax dimers to effect voltage-independent inhibition of Ca(v)3.2 channels. Inhibition requires phosphorylation of Ser(1107), a critical serine residue on the II-III loop of the channel pore protein. S1107A prevents inhibition of unitary currents by recombinant Gbeta(2)gamma(2) dimers but does not disrupt dimer binding nor change its specificity. Gbetagamma dimers released upon receptor activation also require PKA activity for their inhibitory actions. Hence, dopamine inhibition of Ca(v)3.2 whole cell current is precluded by Gbetagamma-scavenger proteins or a peptide that blocks PKA catalytic activity. Fittingly, when used alone at receptor-selective concentrations, D(1) or D(2) agonists do not elicit channel inhibition yet together synergize to inhibit Ca(v)3.2 channel currents. We propose that a dual-receptor regulatory mechanism is used by dopamine to control Ca(v)3.2 channel activity. This mechanism, for example, would be important in aldosterone producing adrenal glomerulosa cells where channel dysregulation would lead to overproduction of aldosterone and consequent cardiac, renal, and brain target organ damage.

Inhibition of human recombinant T‐type calcium channels by the endocannabinoid N‐arachidonoyl dopamine

N-arachidonoyl dopamine (NADA) has complex effects on nociception mediated via cannabinoid CB(1) receptors and the transient receptor potential vanilloid receptor 1 (TRPV1). Anandamide, the prototypic CB(1)/TRPV1 agonist, also inhibits T-type voltage-gated calcium channel currents (I(Ca)). These channels are expressed by many excitable cells, including neurons involved in pain detection and processing. We sought to determine whether NADA and the prototypic arachidonoyl amino acid, N-arachidonoyl glycine (NAGly) modulate T-type I(Ca) Human recombinant T-type I(Ca) (Ca(V)3 channels) expressed in HEK 293 cells and native mouse T-type I(Ca) were examined using standard whole-cell voltage clamp electrophysiology techniques. N-arachidonoyl dopamine completely inhibited Ca(V)3 channels with a rank order of potency (pEC(50)) of Ca(V)3.3 (6.45) > or = Ca(V)3.1 (6.29) > Ca(V)3.2 (5.95). NAGly (10 micromol.L(-1)) inhibited Ca(V)3 I(Ca) by approximately 50% or less. The effects of NADA and NAGly were voltage- but not use-dependent, and both compounds produced significant hyperpolarizing shifts in Ca(V)3 channel steady-state inactivation relationships. By contrast with anandamide, NADA and NAGly had modest effects on Ca(V)3 channel kinetics. Both NAGly and NADA inhibited native T-type I(Ca) in mouse sensory neurons. N-arachidonoyl dopamine and NAGly increase the steady-state inactivation of Ca(V)3 channels, reducing the number of channels available to open during depolarization. These effects occur at NADA concentrations at or below to those affecting CB(1) and TRPV1 receptors. Together with anandamide, the arachidonoyl neurotransmitter amides, NADA and NAGly, represent a new family of endogenous T-type I(Ca) modulators.