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The possible roles of hyperpolarization-activated cyclic nucleotide channels in regulating pacemaker activity in colonic interstitial cells of Cajal.

Shahi PK, Choi S, Zuo DC, Kim MY, Park CG, Kim YD, Lee J, Park KJ, So I, Jun JY - J. Gastroenterol. (2013)

Bottom Line: CsCl, ZD7288, zatebradine, clonidine (HCN channel blockers), and genistein (a tyrosine kinase inhibitor) suppressed the pacemaker activity.In recordings of spontaneous intracellular Ca(2+) [Ca(2+)]i oscillations, rolipram and 8-bromo-cAMP increased [Ca(2+)]i oscillations, whereas SQ-22536, CsCl, ZD7288, and genistein decreased [Ca(2+)]i oscillations.HCN channels in colonic ICCs are tonically activated by basal cAMP production and participate in regulation of pacemaking activity.

View Article: PubMed Central - PubMed

Affiliation: Department of Physiology, College of Medicine, Chosun University, Sesuk-dong, Dong-gu, Gwangju, 501-759, Korea.

ABSTRACT

Background: Hyperpolarization-activated cyclic nucleotide (HCN) channels are pacemaker channels that regulate heart rate and neuronal rhythm in spontaneously active cardiac and neuronal cells. Interstitial cells of Cajal (ICCs) are also spontaneously active pacemaker cells in the gastrointestinal tract. Here, we investigated the existence of HCN channel and its role on pacemaker activity in colonic ICCs.

Methods: We performed whole-cell patch clamp, RT-PCR, and Ca(2+)-imaging in cultured ICCs from mouse mid colon.

Results: SQ-22536 and dideoxyadenosine (adenylate cyclase inhibitors) decreased the frequency of pacemaker potentials, whereas both rolipram (cAMP-specific phosphodiesterase inhibitor) and cell-permeable 8-bromo-cAMP increased the frequency of pacemaker potentials. CsCl, ZD7288, zatebradine, clonidine (HCN channel blockers), and genistein (a tyrosine kinase inhibitor) suppressed the pacemaker activity. RT-PCR revealed expression of HCN1 and HCN3 channels in c-kit and Ano1 positive colonic ICCs. In recordings of spontaneous intracellular Ca(2+) [Ca(2+)]i oscillations, rolipram and 8-bromo-cAMP increased [Ca(2+)]i oscillations, whereas SQ-22536, CsCl, ZD7288, and genistein decreased [Ca(2+)]i oscillations.

Conclusions: HCN channels in colonic ICCs are tonically activated by basal cAMP production and participate in regulation of pacemaking activity.

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Related in: MedlinePlus

Effects of cAMP-related drugs and hyperpolarization-activated cyclic nucleotide (HCN) channel blockers on the spontaneous pacemaker potentials in cultured ICCs from mouse small intestine. SQ-22536 (100 μM) (a), rolipram (100 μM) (b), 8-bromo-cAMP (100 μM) (c), CsCl (5 mM) (d), ZD7288 (10 μM) (e), zatebradine (10 μM) (f), clonidine (100 μM) (g), and genistein (10 μM) (h) all had no effect on pacemaker potentials
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Fig7: Effects of cAMP-related drugs and hyperpolarization-activated cyclic nucleotide (HCN) channel blockers on the spontaneous pacemaker potentials in cultured ICCs from mouse small intestine. SQ-22536 (100 μM) (a), rolipram (100 μM) (b), 8-bromo-cAMP (100 μM) (c), CsCl (5 mM) (d), ZD7288 (10 μM) (e), zatebradine (10 μM) (f), clonidine (100 μM) (g), and genistein (10 μM) (h) all had no effect on pacemaker potentials

Mentions: To evaluate whether HCN channels also involve in intestinal pacemaking, we treated intestinal ICCs with SQ-22536 (100 μM; n = 5), rolipram (100 μM; n = 5), 8-bromo-cAMP (100 μM; n = 9), CsCl (5 mM; n = 6), ZD7288 (10 μM; n = 5), zatebradine (10 μM; n = 5), clonidine (100 μM; n = 5), and genistein (10 μM; n = 6) and performed RT-PCR. We found that all the drugs had no effect on pacemaker potentials of intestinal ICCs (Fig. 7a–h). In RT-PCR analysis, the mRNA transcripts for four HCN channel subtypes were detected in whole-mount cultured intestinal cells (n = 6; Fig. 8a). However, none of the HCN channel subtypes were expressed in cultured c-kit and Ano1 positive intestinal ICCs (n = 10; Fig. 8b).Fig. 8


The possible roles of hyperpolarization-activated cyclic nucleotide channels in regulating pacemaker activity in colonic interstitial cells of Cajal.

Shahi PK, Choi S, Zuo DC, Kim MY, Park CG, Kim YD, Lee J, Park KJ, So I, Jun JY - J. Gastroenterol. (2013)

Effects of cAMP-related drugs and hyperpolarization-activated cyclic nucleotide (HCN) channel blockers on the spontaneous pacemaker potentials in cultured ICCs from mouse small intestine. SQ-22536 (100 μM) (a), rolipram (100 μM) (b), 8-bromo-cAMP (100 μM) (c), CsCl (5 mM) (d), ZD7288 (10 μM) (e), zatebradine (10 μM) (f), clonidine (100 μM) (g), and genistein (10 μM) (h) all had no effect on pacemaker potentials
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

Show All Figures
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Fig7: Effects of cAMP-related drugs and hyperpolarization-activated cyclic nucleotide (HCN) channel blockers on the spontaneous pacemaker potentials in cultured ICCs from mouse small intestine. SQ-22536 (100 μM) (a), rolipram (100 μM) (b), 8-bromo-cAMP (100 μM) (c), CsCl (5 mM) (d), ZD7288 (10 μM) (e), zatebradine (10 μM) (f), clonidine (100 μM) (g), and genistein (10 μM) (h) all had no effect on pacemaker potentials
Mentions: To evaluate whether HCN channels also involve in intestinal pacemaking, we treated intestinal ICCs with SQ-22536 (100 μM; n = 5), rolipram (100 μM; n = 5), 8-bromo-cAMP (100 μM; n = 9), CsCl (5 mM; n = 6), ZD7288 (10 μM; n = 5), zatebradine (10 μM; n = 5), clonidine (100 μM; n = 5), and genistein (10 μM; n = 6) and performed RT-PCR. We found that all the drugs had no effect on pacemaker potentials of intestinal ICCs (Fig. 7a–h). In RT-PCR analysis, the mRNA transcripts for four HCN channel subtypes were detected in whole-mount cultured intestinal cells (n = 6; Fig. 8a). However, none of the HCN channel subtypes were expressed in cultured c-kit and Ano1 positive intestinal ICCs (n = 10; Fig. 8b).Fig. 8

Bottom Line: CsCl, ZD7288, zatebradine, clonidine (HCN channel blockers), and genistein (a tyrosine kinase inhibitor) suppressed the pacemaker activity.In recordings of spontaneous intracellular Ca(2+) [Ca(2+)]i oscillations, rolipram and 8-bromo-cAMP increased [Ca(2+)]i oscillations, whereas SQ-22536, CsCl, ZD7288, and genistein decreased [Ca(2+)]i oscillations.HCN channels in colonic ICCs are tonically activated by basal cAMP production and participate in regulation of pacemaking activity.

View Article: PubMed Central - PubMed

Affiliation: Department of Physiology, College of Medicine, Chosun University, Sesuk-dong, Dong-gu, Gwangju, 501-759, Korea.

ABSTRACT

Background: Hyperpolarization-activated cyclic nucleotide (HCN) channels are pacemaker channels that regulate heart rate and neuronal rhythm in spontaneously active cardiac and neuronal cells. Interstitial cells of Cajal (ICCs) are also spontaneously active pacemaker cells in the gastrointestinal tract. Here, we investigated the existence of HCN channel and its role on pacemaker activity in colonic ICCs.

Methods: We performed whole-cell patch clamp, RT-PCR, and Ca(2+)-imaging in cultured ICCs from mouse mid colon.

Results: SQ-22536 and dideoxyadenosine (adenylate cyclase inhibitors) decreased the frequency of pacemaker potentials, whereas both rolipram (cAMP-specific phosphodiesterase inhibitor) and cell-permeable 8-bromo-cAMP increased the frequency of pacemaker potentials. CsCl, ZD7288, zatebradine, clonidine (HCN channel blockers), and genistein (a tyrosine kinase inhibitor) suppressed the pacemaker activity. RT-PCR revealed expression of HCN1 and HCN3 channels in c-kit and Ano1 positive colonic ICCs. In recordings of spontaneous intracellular Ca(2+) [Ca(2+)]i oscillations, rolipram and 8-bromo-cAMP increased [Ca(2+)]i oscillations, whereas SQ-22536, CsCl, ZD7288, and genistein decreased [Ca(2+)]i oscillations.

Conclusions: HCN channels in colonic ICCs are tonically activated by basal cAMP production and participate in regulation of pacemaking activity.

Show MeSH
Related in: MedlinePlus