Ca^(2+) cannel subtypes in the sympathetic major pelvic ganglion (MPG) neurons of the rat

Hong, Sung Won,Kim, Young Kyu 東國大學校醫學硏究所 2004 東國醫學 Vol.11 No.1

세포내의 칼슘은 신경전달물질의 분비, 이온 통로의 개폐와 조절과 같은 신경세포의 기능에 있어서 매우 중요한 기능을 하고 있다. 신경세포 안으로의 칼슘의 유입은 주로 칼슘통로를 통하여 일어나므로, 칼슘통로의 동정과 그 종류의 분리는 세포내 칼슘농도에 의하여 야기되는 신경세포의 기능 조절을 이해함에 있어서 매우 중요하다. 본 연구에서는 흰쥐의 골반신경절(MPG)에서 나타나는 교감신경세포의 칼슘통로의 유무와 그 종류들을 새로이 분리 배양된 세포(배양 4시간 후부터)에서 전기생리학적 또한 약리학적 방법론들을 사용하여 규명하였다. MPG 교감신경세포들에서는 LVA T-형과 HVA 칼슘통로 모두가 발현되고 있으며, LVA T-type 칼슘통로는 -60 mV에서 활성화되기 시작하였고 HVA 칼슘통로는 보다 높은 -40mV에서 활성화되기 시작하였다. LVA T-형 칼슘통로는 Ni^(2+)에 더 잘 억제되었으며, HVA칼슘통로는 Ni^(2+)(IC_{50}=599 μM)에 비하여 Cd^(2+)(IC_{50}=8.2 μM)에 더 민감히 억제되었다. 또한 HVA 칼슘 통로들은 특정 유기 억제약물들을 사용하여 세부 이종류로 규명하였다. 연속적으로 칼슘통로 억제약물인 1 μM ω-conotoxin GVIA (N-typ), 1 μM ω-conotoxin MVITC (P/Qtype), 10 μM nimodipine(L-type), 그리고 200 nM SNX-482 (R-type)를 투여하였을 시에 각각의 억제 약물들에 의하여 억제되는 칼슘통로들은 각각 N-type이 70.2%, P/Q-type이 7.6%, L-type이 11.2%, 그리고 R-type이 11.1%로 나타났다. 따라서 흰쥐 골발신경절에서 나타나는 교감신경세포에는 LVA T-형 및 HVA N-, L-, P/Q,R-형 칼슘통로가 발현되고 있으며, 전체 칼슘통로 중에서 N-형 칼슘통로가 70% 이상을 차지하는 주된 칼슘통로이다. Intracellular Ca^(2+) plays an important role in various cellular functions such as transmitter release and modulation of opening ion channels. Since the voltage-gated Ca^(2+)channel is a major route for Ca^(2+) entry into the cell, identification of Ca^(2+) subtypes expressed in a neuron is essential to understand the regulation of some specific neuronal functions triggered by intracellular Ca^(2+). The subtypes of Ca^(2+) channels in sympathetic neurons of the male rat major pelvic ganglion (MPG) were electrophysiologicdy and pharmacologiacally identified from acutely dissociated neurons using whole-cell patch-clamp technique and both inorganic and specific organic Ca^(2+) channel blockers. The MFG sympathetic neurons appeared to have both low-voltage-activated (LVA) and high-voltage-activated (HVA) Ca^(2+) channels, whereas parasympathetic neuron did not. In the sympathetic neurons, the LVA T-type Ca^(2+) channels became activated at around -60 mV and more sensitive to Ni^(2+) than Cd^(2+), whereas the HVA Ca^(2+) channels are activated at -40 mV and more sensitive to Cd^(2+) (IC_(50) = 8.2 μM) than to Ni^(2+) (IC_(50) = 599 μM). In addition, the HVA Ca^(2+) channels are further classified into subtypes using specific organic Ca^(2+) channel blockers including 10-conotoxin GVIA (N-type), 10-conotoxin MVIIC (P/Q-type), 10 μM nimodipine (Ltype), and 200 nM SNX-482 (R-type). The HVA Ca^(2+) channel subtypes expressed in the MPG sympathetic neurons were consisted of 70.2% N-type, 7.6% P/Q-type, 11.2% Ltype, and 11.l% R-type Ca^(2+) channels. The present study demonstrated that the sympathetic neuron contains both LVA T-type and HVA Ca^(2+) channels. The present study also showed that the N-type is a major subtype of Ca^(2+)' channels and the presence of R-type Ca^(2+) channel in the sympathetic MPG neurons of the rat.

Characterization of Calcium Release Channel (Ryanodine Receptor) in Sarcoplasmic Reticulum of Crustacean Skeletal Muscle

석정호,정정구,허강민,이재흔,Seok, Jeong-Ho,Jung, Jung-Koo,Hur, Gang-Min,Lee, Jae-Heun The Korean Society of Pharmacology 1994 대한약리학잡지 Vol.30 No.1

갑각류 골격근의 SR에서 칼슘유리 channel protein complex의 성격을 규명하기 위해 민물가재 및/또는 바다가재의 SR vesicles을 분리하여 $^{45}Ca$ 유리, $[^3H]ryanodine$결합, 및 immunoblot 실험을 실시하여 다음과 같은 결과를 얻었다. 1.민물가재 SR의 $[^3H]ryanodine$결합 실험에서 민물가재 SR의 maximal binding site및 affinity모두 바다가재에서 보다 낮았으나, high affinity binding site이었다. Extravesicles 칼슘농도를 증가시켰을 때 $[^3H]ryanodine$결합은 약간 증가되었으나, AMP나 AMP와 caffeine을 동시에 첨가하였을 때는 현저히 증가되었다(p<0.05). 이런 증가 현상은 $MgCl_2$나 tetracaine으로 유의성 있게 억제되었으나(p<0.001), ruthenium red에 의해서는 약간 억제되었다. 2.민물가재 SR을 전기영동하였을 때 바다가재의 ryanodine receptor band (HMWBr)와 비슷하나 포유류의 것(HMWBS) 보다는 약간 빠른 mobility를 나타낸다. 3.바다가재 HMWBr에 대한 polyclonal Ab를 이용한 민물가재, 바다가재 및 토끼 골격근의 칼슘유리 channel간의 면역학적 교차반응에서 민물가재와 바다가재의 칼슘유리 channel 간에는 교차반응이 있었으나, 포유류의 것과는 아무런 반응이 없었다. 4.민물가재 SR에서 $^{45}Ca$유리는 extravesicles의 칼슘농도 증가에 따라서 증가되었고, 낮은 외부 칼슘 농도에서 바다가재 보다 빠르게 일어났으나, AMP와 caffeine에 의해 영향을 받지 않았고, $MgCl_2$와 tetracaine으로 약간($3{\sim}8%$) 그리고 고농도의 ruthenium red로 중등도(23%) 억제되었다. 이상의 실험성적으로 갑각류 칼슘유리 channel protein은 포유류의 것과는 기능적으로나 면역학적으로 매우 다른 특징을 가지고 있고, 민물가재와 바다가재 칼슘유리 channel은 서로 유사한 특징을 갖지만, 민물가재의 칼슘유리 channel이 바다가재의 것보다 외부칼슘에 예민한 기능을 갖는 것으로 사료된다. To characterize the SR Ca-release channel protein complex of crustacean, $^{45}Ca-release,\;[^3H]ryanodine$ binding, and immunoblot studies were carried out in the crayfish and/or lobster skeletal sarcoplasmic reticulum. Bmax and affinity of crayfish SR to ryanodine were lower than those of lobster SR. AMP (5mM) increased $[^3H]ryanodine$ binding significantly in both vesicles (P<0.05). $Mg^{2+}$(5mM) or tetracaine(1mM) inhibited $[^3H]ryanodine$ binding significantly in both vesicles (P<0.001), but ruthenium red $(10\;{\mu}M)$ inhibited it moderately. In SDS polyacrylamide gel electrophoretic analysis of crayfish SR vesicles, there was a high molecular weight band that showed similar mobility with Ca-release channel protein of lobster skeletal SR, but more rapid mobility (HMWBr) than that of rabbit skeletal SR (HMWBS). Immunoblot analysis showed that polyclonal Ab to lobster skeletal SR Ca-release channel protein was react with HMWBr of crayfish skeletal SR, but not with that of HMWBs of rabbit skeletal SR. ^{45}Ca-release from crayfish skeletal SR vesicles was increased by the increase of extravesicular calcium from $1{\mu}M$ to 1mM. This Ca-release phenomenon was similar, but more sensitive in the low concentration of $Ca^{2+}$, compared to that from lobster SR vesicles. AMP (5mM) or caffeine (10mM) did not affect to $^{45}Ca-release.\;^{45}Ca-release$ was inhibited slightly ($3{\sim}8%\;by\;Mg^{2+}$) (5mM) or tetracaine (1mM), and moderately (23%) by high concentration of ruthenium red $(300\;{\mu}M)$. From the above results, it is suggested that SR Ca-release channel protein of crustacean has different properties from that of the rabbit, and similar properties between crayfish and lobster in functional and immunological aspects, but Ca-release via crayfish channel may be more sensitive to calcium.

Activation of Lysophosphatidic Acid Receptor Is Coupled to Enhancement of Ca<SUP>2+</SUP>-Activated Potassium Channel Currents

Sun-Hye Choi,Byung-Hwan Lee,Hyeon-Joong Kim,Sung-Hee Hwang,Sang-Mok Lee,Seung-Yeol Nah 대한생리학회-대한약리학회 2013 The Korean Journal of Physiology & Pharmacology Vol.17 No.3

The calcium-activated K⁺ (BK_Ca) channel is one of the potassium-selective ion channels that are present in the nervous and vascular systems. Ca²⁺ is the main regulator of BK_Ca channel activation. The BK_Cachannel contains two high affinity Ca²⁺ binding sites, namely, regulators of K⁺ conductance, RCK1 and the Ca²⁺ bowl. Lysophosphatidic acid (LPA, 1-radyl-2-hydroxy-sn-glycero-3-phosphate) is one of the neurolipids. LPA affects diverse cellular functions on many cell types through G protein- coupled LPA receptor subtypes. The activation of LPA receptors induces transient elevation of intracellular Ca²⁺ levels through diverse G proteins such as GՁ_q/11, GՁ_i, GՁ_12/13, and GՁs and the related signal transduction pathway. In the present study, we examined LPA effects on BK_Cachannel activity expressed in Xenopus oocytes, which are known to endogenously express the LPA receptor. Treatment with LPA induced a large outward current in a reversible and concentration-dependent manner. However, repeated treatment with LPA induced a rapid desensitization, and the LPA receptor antagonist Ki16425 blocked LPA action. LPA-mediated BK_Ca channel activation was also attenuated by the PLC inhibitor U-73122, IP₃inhibitor 2-APB, Ca²⁺ chelator BAPTA, or PKC inhibitor calphostin. In addition, mutations in RCK1 and RCK2 also attenuated LPA-mediated BK_Ca channel activation. The present study indicates that LPA-mediated activation of the BK_Ca channel is achieved through the PLC, IP₃, Ca²⁺, and PKC pathway and that LPA-mediated activation of the BK_Ca channel could be one of the biological effects of LPA in the nervous and vascular systems.

Acetylcholine Induces Hyperpolarization Mediated by Activation of K<SUB>(Ca)</SUB> Channels in Cultured Chick Myoblasts

Doyun Lee,Jaehee Han,Jae-Yong Park 대한생리학회-대한약리학회 2005 The Korean Journal of Physiology & Pharmacology Vol.9 No.1

Our previous report demonstrated that chick myoblasts are equipped with Ca<SUP>2⁢</SUP>-permeable stretch- activated channels and Ca<SUP>2⁢</SUP>-activated potassium channels (K<SUB>Ca</SUB>), and that hyperpolarization-induced by K<SUB>Ca</SUB> channels provides driving force for Ca<SUP>2⁢ </SUP>influx through the stretch-activated channels into the cells. Here, we showed that acetylcholine (ACh) also hyperpolarized the membrane of cultured chick myoblasts, suggesting that nicotinic acetylcholine receptor (nAChR) may be another pathway for Ca<SUP>2⁢</SUP> influx. Under cell-attatched patch configuration, ACh increased the open probability of K<SUB>Ca</SUB> channels from 0.007 to 0.055 only when extracellular Ca<SUP>2⁢</SUP> was present. Nicotine, a nAChR agonist, increased the open probability of K<SUB>Ca</SUB> channels from 0.008 to 0.023, whereas muscarine failed to do so. Since the activity of K<SUB>Ca</SUB> channel is sensitive to intracellular Ca<SUP>2⁢</SUP> level, nAChR seems to be capable of inducing Ca<SUP>2⁢</SUP> influx. Using the Ca<SUP>2⁢</SUP> imaging analysis, we were able to provide direct evidence that ACh induced Ca<SUP>2⁢</SUP> influx from extracellular solution, which was dramatically increased by valinomycin-mediated hyperpolarization. In addition, ACh hyperpolarized the membrane potential from ⁣12.5⁑3 to ⁣31.2⁑5 mV by generating the outward current through K<SUB>Ca</SUB> channels. These results suggest that activation of nAChR increases Ca<SUP>2⁢</SUP> influx, which activates K<SUB>Ca</SUB> channels, thereby hyperpolarizing the membrane potential in chick myoblasts.

Contribution of Different Types of $Ca^{2+}$ channels to Catecholamine Secretion in Rat Adrenal Chromaffin Cells

Goo, Yang-Soak,Roh, Jin-A,Lee, Jung-Hwa,Chao, Eun-Jong Korean Society of Medical Physics 1997 의학물리 Vol.8 No.1

Adrenal chromaffin cells secrete catecholamine in response to acetylcholine. The secretory response has absolute requirement for extracellular calcium, indication that $Ca^{2+}$ influx through voltage dependent $Ca^{2+}$ channel (VDCC) is the primary trigger of the secretion cascade. Although the existence of various types of $Ca^{2+}$ channels has been explored using patch clamp technique in adrenal chromaffin cells, the contribution of different types of $Ca^{2+}$ channels to catecholamine secretion remains to be established. To investigate the quantative contribution of different types of $Ca^{2+}$ channels to cate-cholamine secretion, $Ca^{2+}$ current($I_{Ca}$) and the resultant membrane capacitance increment($\Delta{C}_{m}$) were simultaneoulsy measured. Software based phasor detector technique was used to monitor $\Delta{C}_{m}$. After blockade of L type VDCC with nicardipine (1$\mu$M), $I_{ca}$ was blocked to 43.85$\pm$6.72%(mean$\pm$SEM) of control and the resultant ㅿC$_{m}$ was reduced ot 30.10$\pm$16.44% of control. In the presence of nicardipine and $\omega$-conotoxin in GVIA(l$\mu$M), an N type VDCC antagonist, $I_{ca}$ was blocked to 11.62$\pm$2.96% of control and the resultant $\Delta{C}_{m}$ was reduced to 26.13$\pm$8.25% of control. Finally, in the presence of L, N, and P type $Ca^{2\pm}$ channel antagonists(nicardipine, $\omega$-Conotoxin GVIA, and $\omega$-agatoxin IVA, respectively), $I_{ca}$ and resultant $\Delta{C}_{m}$ were almost completely blocked. From the observation of parallel effects of $Ca^{2+}$ channel antagonists on $I_{ca}$ and $\Delta{C}_{m}$, it was concluded that L, N, and also P type $Ca^{2+}$ channels served and $Ca^{2+}$ source for exocytosis and no difference was observed in their efficiency to evoke exocytosis amost L, N, and P type $Ca^{2+}$ channels.

Acetylcholine Induces Hyperpolarization Mediated by Activation of $K_{(ca)}$ Channels in Cultured Chick Myoblasts

Lee, Do-Yun,Han, Jae-Hee,Park, Jae-Yong The Korean Society of Pharmacology 2005 The Korean Journal of Physiology & Pharmacology Vol.9 No.1

Our previous report demonstrated that chick myoblasts are equipped with $Ca^{2+}$-permeable stretchactivated channels and $Ca^{2+}-activated$ potassium channels ($K_{Ca}$), and that hyperpolarization-induced by $K_{Ca}$ channels provides driving force for $Ca^{2+}$ influx through the stretch-activated channels into the cells. Here, we showed that acetylcholine (ACh) also hyperpolarized the membrane of cultured chick myoblasts, suggesting that nicotinic acetylcholine receptor (nAChR) may be another pathway for $Ca^{2+}$ influx. Under cell-attatched patch configuration, ACh increased the open probability of $K_{Ca}$ channels from 0.007 to 0.055 only when extracellular $Ca^{2+}$ was present. Nicotine, a nAChR agonist, increased the open probability of $K_{Ca}$ channels from 0.008 to 0.023, whereas muscarine failed to do so. Since the activity of $K_{Ca}$ channel is sensitive to intracellular $Ca^{2+}$ level, nAChR seems to be capable of inducing $Ca^{2+}$ influx. Using the $Ca^{2+}$ imaging analysis, we were able to provide direct evidence that ACh induced $Ca^{2+}$ influx from extracellular solution, which was dramatically increased by valinomycin-mediated hyperpolarization. In addition, ACh hyperpolarized the membrane potential from $-12.5{\pm}3$ to $-31.2{\pm}5$ mV by generating the outward current through $K_{Ca}$ channels. These results suggest that activation of nAChR increases $Ca^{2+}$ influx, which activates $K_{Ca}$ channels, thereby hyperpolarizing the membrane potential in chick myoblasts.

Chronic Ca2+ influx through voltage-dependent Ca2+ channels enhance delayed rectifier K+ currents via activating Src family tyrosine kinase in rat hippocampal neurons

양윤실,전상찬,김동관,은수용,정성철 대한약리학회 2017 The Korean Journal of Physiology & Pharmacology Vol.21 No.2

Excessive influx and the subsequent rapid cytosolic elevation of Ca2+ in neurons is the major cause to induce hyperexcitability and irreversible cell damage although it is an essential ion for cellular signalings. Therefore, most neurons exhibit several cellular mechanisms to homeostatically regulate cytosolic Ca2+ level in normal as well as pathological conditions. Delayed rectifier K+ channels (IDR channels) play a role to suppress membrane excitability by inducing K+ outflow in various conditions, indicating their potential role in preventing pathogenic conditions and cell damage under Ca2+-mediated excitotoxic conditions. In the present study, we electrophysiologically evaluated the response of IDR channels to hyperexcitable conditions induced by high Ca2+ pretreatment (3.6 mM, for 24 hours) in cultured hippocampal neurons. In results, high Ca2+-treatment significantly increased the amplitude of IDR without changes of gating kinetics. Nimodipine but not APV blocked Ca2+-induced IDR enhancement, confirming that the change of IDR might be targeted by Ca2+ influx through voltage-dependent Ca2+ channels (VDCCs) rather than NMDA receptors (NMDARs). The VDCC-mediated IDR enhancement was not affected by either Ca2+-induced Ca2+ release (CICR) or small conductance Ca2+-activated K+ channels (SK channels). Furthermore, PP2 but not H89 completely abolished IDR enhancement under high Ca2+ condition, indicating that the activation of Src family tyrosine kinases (SFKs) is required for Ca2+-mediated IDR enhancement. Thus, SFKs may be sensitive to excessive Ca2+ influx through VDCCs and enhance IDR to activate a neuroprotective mechanism against Ca2+-mediated hyperexcitability in neurons.

Chronic Ca²⁺ influx through voltage-dependent Ca²⁺ channels enhance delayed rectifier K⁺ currents via activating Src family tyrosine kinase in rat hippocampal neurons

Yang, Yoon-Sil,Jeon, Sang-Chan,Kim, Dong-Kwan,Eun, Su-Yong,Jung, Sung-Cherl The Korean Society of Pharmacology 2017 The Korean Journal of Physiology & Pharmacology Vol.21 No.2

Excessive influx and the subsequent rapid cytosolic elevation of $Ca^{2+}$ in neurons is the major cause to induce hyperexcitability and irreversible cell damage although it is an essential ion for cellular signalings. Therefore, most neurons exhibit several cellular mechanisms to homeostatically regulate cytosolic $Ca^{2+}$ level in normal as well as pathological conditions. Delayed rectifier $K^+$ channels ($I_{DR}$ channels) play a role to suppress membrane excitability by inducing $K^+$ outflow in various conditions, indicating their potential role in preventing pathogenic conditions and cell damage under $Ca^{2+}$-mediated excitotoxic conditions. In the present study, we electrophysiologically evaluated the response of $I_{DR}$ channels to hyperexcitable conditions induced by high $Ca^{2+}$ pretreatment (3.6 mM, for 24 hours) in cultured hippocampal neurons. In results, high $Ca^{2+}$-treatment significantly increased the amplitude of $I_{DR}$ without changes of gating kinetics. Nimodipine but not APV blocked $Ca^{2+}$-induced $I_{DR}$ enhancement, confirming that the change of $I_{DR}$ might be targeted by $Ca^{2+}$ influx through voltage-dependent $Ca^{2+}$ channels (VDCCs) rather than NMDA receptors (NMDARs). The VDCC-mediated $I_{DR}$ enhancement was not affected by either $Ca^{2+}$-induced $Ca^{2+}$ release (CICR) or small conductance $Ca^{2+}$-activated $K^+$ channels (SK channels). Furthermore, PP2 but not H89 completely abolished $I_{DR}$ enhancement under high $Ca^{2+}$ condition, indicating that the activation of Src family tyrosine kinases (SFKs) is required for $Ca^{2+}$-mediated $I_{DR}$ enhancement. Thus, SFKs may be sensitive to excessive $Ca^{2+}$ influx through VDCCs and enhance $I_{DR}$ to activate a neuroprotective mechanism against $Ca^{2+}$-mediated hyperexcitability in neurons.

The mitochondrial Ca²⁺-activated K⁺ channel activator, NS 1619 inhibits L-type Ca²⁺ channels in rat ventricular myocytes

Park, Won Sun,Kang, Sung Hyun,Son, Youn Kyoung,Kim, Nari,Ko, Jae-Hong,Kim, Hyoung Kyu,Ko, Eun A.,Kim, Chi Dae,Han, Jin Elsevier 2007 Biochemical and biophysical research communication Vol.362 No.1

<P><B>Abstract</B></P> <P>We examined the effects of the mitochondrial Ca<SUP>2+</SUP>-activated K<SUP>+</SUP> (mitoBK<SUB>Ca</SUB>) channel activator NS 1619 on L-type Ca<SUP>2+</SUP> channels in rat ventricular myocytes. NS 1619 inhibited the Ca<SUP>2+</SUP> current in a dose-dependent manner. NS 1619 shifted the activation curve to more positive potentials, but did not have a significant effect on the inactivation curve. Pretreatment with inhibitors of membrane BK<SUB>Ca</SUB> channel, mitoBK<SUB>Ca</SUB> channel, protein kinase C, protein kinase A, and protein kinase G had little effect on the Ca<SUP>2+</SUP> current and did not alter the inhibitory effect of NS 1619 significantly. The application of additional NS 1619 in the presence of isoproterenol, a selective β-adrenoreceptor agonist, reduced the Ca<SUP>2+</SUP> current to approximately the same level as a single application of NS 1619. In conclusion, our results suggest that NS 1619 inhibits the Ca<SUP>2+</SUP> current independent of the mitoBK<SUB>Ca</SUB> channel and protein kinases. Since NS 1619 is widely used to study mitoBK<SUB>Ca</SUB> channel function, it is essential to verify these unexpected effects of NS 1619 before experimental data can be interpreted accurately.</P>

Effects of Ca²⁺-Activated Cl^- Channel ANO1inhibitors on Pacemaker Activity in Interstitial Cells of Cajal

Choi, Seok,Kang, Hyun Goo,Wu, Mei Jin,Jiao, Han Yi,Shin, Dong Hoon,Hong, Chansik,Jun, Jae Yeoul S. Karger AG 2019 CELLULAR PHYSIOLOGY AND BIOCHEMISTRY Vol.51 No.6

<P><B><I>Background/Aims:</I></B> Anoctamin1 (Ca<SUP>2+</SUP>-activated Cl<SUP>-</SUP> channel, ANO1) is a specific marker of the interstitial cells of Cajal (ICC) in the gastrointestinal tract, and are candidate proteins that can function as pacemaker channels. Recently, novel selective ANO1 inhibitors were discovered and used to study Ca<SUP>2+</SUP>-activated Cl<SUP>-</SUP> channels. Therefore, to investigate whether ANO1 channels function as pacemaker channels, selective ANO1 inhibitors were tested with respect to the pacemaker potentials in ICC. <B><I>Methods:</I></B> Whole-cell patch-clamp recording, RT-PCR, and intracellular Ca<SUP>2+</SUP> ([Ca<SUP>2+</SUP>]<SUB>i</SUB>) imaging were performed in cultured ICC obtained from mice. <B><I>Results:</I></B> Though CaCCinh-A01 (5 µM), T16Ainh-A01 (5 µM), and MONNA (5 µM) (selective ANO1 inhibitors) blocked the generation of pacemaker potentials in colonic ICC, they did not do so in small intestinal ICC. Though nifulmic acid (10 µM) and DIDS (10 µM) (classical Ca<SUP>2+</SUP>-activated Cl<SUP>-</SUP> channel inhibitors) also had no effect in small intestinal ICC, they suppressed the generation of pacemaker potentials in colonic ICC. In addition, knockdown of ANO1 reduced the pacemaker potential frequency in colonic ICC alone. Though ANO1 inhibitors suppressed [Ca<SUP>2+</SUP>]<SUB>i</SUB> oscillations in colonic ICC, they did not do so in small intestinal ICC. T-type Ca<SUP>2+</SUP> channels were expressed in the both the small intestinal and colonic ICC, but mibefradil (5 µM) and NiCl<SUB>2</SUB> (30 µM) (T-type Ca<SUP>2+</SUP> channel inhibitors) inhibited the generation of pacemaker potentials in colonic ICC alone. Conclusion: These results indicate that though ANO1 and T-type Ca<SUP>2+</SUP> channels participate in generating pacemaker potentials in colonic ICC, they do not do so in small intestinal ICC. Therefore, the mechanisms underlying pacemaking in ICC might be different in the small intestine and the colon.</P>