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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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Effects of hyperpolarization-activated cyclic nucleotide (HCN) channel blockers on the spontaneous pacemaker potentials in cultured ICCs of the mouse colon. CsCl (5 mM) (a), ZD7288 (10 μM) (b), zatebradine (10 μM) (c), clonidine (100 μM) (d), and genistein (10 μM) (e). All traces showed the reduced frequency of pacemaker potentials. The effects of these drugs on pacemaker potentials are summarized in f and g. Bars represent mean ± SE values (p < 0.05)
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Fig4: Effects of hyperpolarization-activated cyclic nucleotide (HCN) channel blockers on the spontaneous pacemaker potentials in cultured ICCs of the mouse colon. CsCl (5 mM) (a), ZD7288 (10 μM) (b), zatebradine (10 μM) (c), clonidine (100 μM) (d), and genistein (10 μM) (e). All traces showed the reduced frequency of pacemaker potentials. The effects of these drugs on pacemaker potentials are summarized in f and g. Bars represent mean ± SE values (p < 0.05)

Mentions: To evaluate whether the cAMP-dependent regulation of pacemaker activity was mediated through HCN channels, we treated ICCs with HCN channel blockers such as CsCl (5 mM; n = 6), ZD7288 (10 μM; n = 8), zatebradine (10 μM; n = 8), and clonidine (100 μM; n = 6) [29]. In addition, there is a report that Src tyrosine kinase inhibitor, genistein, modulates HCN channels [30], we also treated genistein (10 μM; n = 5) to pacemaker potential generating colonic ICCs. We found that CsCl, ZD7288, zatebradine, clonidine, and genistein all decreased the frequency of pacemaker potentials (Fig. 4a–e). The responses to the above drugs on the pacemaker potentials in ICCs are summarized in Fig. 4f and g. The values of the frequency induced by the above drugs were significantly different from control values. These results suggest that the cAMP-dependent regulation of pacemaker activity may be mediated through HCN channels.Fig. 4


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 hyperpolarization-activated cyclic nucleotide (HCN) channel blockers on the spontaneous pacemaker potentials in cultured ICCs of the mouse colon. CsCl (5 mM) (a), ZD7288 (10 μM) (b), zatebradine (10 μM) (c), clonidine (100 μM) (d), and genistein (10 μM) (e). All traces showed the reduced frequency of pacemaker potentials. The effects of these drugs on pacemaker potentials are summarized in f and g. Bars represent mean ± SE values (p < 0.05)
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

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Fig4: Effects of hyperpolarization-activated cyclic nucleotide (HCN) channel blockers on the spontaneous pacemaker potentials in cultured ICCs of the mouse colon. CsCl (5 mM) (a), ZD7288 (10 μM) (b), zatebradine (10 μM) (c), clonidine (100 μM) (d), and genistein (10 μM) (e). All traces showed the reduced frequency of pacemaker potentials. The effects of these drugs on pacemaker potentials are summarized in f and g. Bars represent mean ± SE values (p < 0.05)
Mentions: To evaluate whether the cAMP-dependent regulation of pacemaker activity was mediated through HCN channels, we treated ICCs with HCN channel blockers such as CsCl (5 mM; n = 6), ZD7288 (10 μM; n = 8), zatebradine (10 μM; n = 8), and clonidine (100 μM; n = 6) [29]. In addition, there is a report that Src tyrosine kinase inhibitor, genistein, modulates HCN channels [30], we also treated genistein (10 μM; n = 5) to pacemaker potential generating colonic ICCs. We found that CsCl, ZD7288, zatebradine, clonidine, and genistein all decreased the frequency of pacemaker potentials (Fig. 4a–e). The responses to the above drugs on the pacemaker potentials in ICCs are summarized in Fig. 4f and g. The values of the frequency induced by the above drugs were significantly different from control values. These results suggest that the cAMP-dependent regulation of pacemaker activity may be mediated through HCN channels.Fig. 4

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