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Pituitary Adenylate Cyclase-activating Polypeptide Inhibits Pacemaker Activity of Colonic Interstitial Cells of Cajal.

Wu MJ, Kee KH, Na J, Kim SW, Bae Y, Shin DH, Choi S, Jun JY, Jeong HS, Park JS - Korean J. Physiol. Pharmacol. (2015)

Bottom Line: The effects of SQ-22536 on pacemaker potential frequency and membrane hyperpolarization were rescued by co-treatment with glibenclamide (an ATP-sensitive K(+) channel blocker).However, neither N (G)-nitro-L-arginine methyl ester (L-NAME, a competitive inhibitor of NO synthase) nor 1H-[1,2,4]oxadiazolo[4,3-α]quinoxalin-1-one (ODQ, an inhibitor of guanylate cyclase) had any effect on PACAP-induced activity.These results provide evidence of a physiological role for PACAP in regulating gastrointestinal (GI) motility through the modulation of ICC activity.

View Article: PubMed Central - PubMed

Affiliation: Department of Physiology, Chonnam National University Medical School, Gwangju 501-757, Korea.

ABSTRACT
This study aimed to investigate the effect of pituitary adenylate cyclase-activating peptide (PACAP) on the pacemaker activity of interstitial cells of Cajal (ICC) in mouse colon and to identify the underlying mechanisms of PACAP action. Spontaneous pacemaker activity of colonic ICC and the effects of PACAP were studied using electrophysiological recordings. Exogenously applied PACAP induced hyperpolarization of the cell membrane and inhibited pacemaker frequency in a dose-dependent manner (from 0.1 nM to 100 nM). To investigate cyclic AMP (cAMP) involvement in the effects of PACAP on ICC, SQ-22536 (an inhibitor of adenylate cyclase) and cell-permeable 8-bromo-cAMP were used. SQ-22536 decreased the frequency of pacemaker potentials, and cell-permeable 8-bromo-cAMP increased the frequency of pacemaker potentials. The effects of SQ-22536 on pacemaker potential frequency and membrane hyperpolarization were rescued by co-treatment with glibenclamide (an ATP-sensitive K(+) channel blocker). However, neither N (G)-nitro-L-arginine methyl ester (L-NAME, a competitive inhibitor of NO synthase) nor 1H-[1,2,4]oxadiazolo[4,3-α]quinoxalin-1-one (ODQ, an inhibitor of guanylate cyclase) had any effect on PACAP-induced activity. In conclusion, this study describes the effects of PACAP on ICC in the mouse colon. PACAP inhibited the pacemaker activity of ICC by acting through ATP-sensitive K(+) channels. These results provide evidence of a physiological role for PACAP in regulating gastrointestinal (GI) motility through the modulation of ICC activity.

No MeSH data available.


Effects of various concentrations of pituitary adenylate cyclase-activating peptide (PACAP) on pacemaker potentials recorded in cultured interstitial cells of Cajal (ICC) from mouse colon. (A), (B), (C), and (D) show pacemaker potentials of ICC exposed to PACAP (0.1 nM, 1 nM, 10 nM, or 100 nM) under current-clamp mode (I=0). Vertical solid lines represent the amplitude of pacemaker potentials and horizontal solid lines represent the duration of recording (s) of pacemaker potentials. The dotted lines indicate the resting membrane potential. (E) and (F) summarize the effects of PACAP on pacemaker potentials in ICC. Bars represent the means±SE. *Asterisks indicate a statistically significant difference from controls (p<0.05). Con, control.
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Figure 2: Effects of various concentrations of pituitary adenylate cyclase-activating peptide (PACAP) on pacemaker potentials recorded in cultured interstitial cells of Cajal (ICC) from mouse colon. (A), (B), (C), and (D) show pacemaker potentials of ICC exposed to PACAP (0.1 nM, 1 nM, 10 nM, or 100 nM) under current-clamp mode (I=0). Vertical solid lines represent the amplitude of pacemaker potentials and horizontal solid lines represent the duration of recording (s) of pacemaker potentials. The dotted lines indicate the resting membrane potential. (E) and (F) summarize the effects of PACAP on pacemaker potentials in ICC. Bars represent the means±SE. *Asterisks indicate a statistically significant difference from controls (p<0.05). Con, control.

Mentions: We examined whether exogenous exposure to PACAP triggered dose-dependent effects on ICC pacemaker potentials in current-clamp mode (I=0). Under a current clamp, ICC generated spontaneous pacemaker potentials. The application of 0.1 nM or 1 nM PACAP induced slight hyperpolarization with reduction of frequency (Fig. 2A and B). Next, we found that pacemaker potentials were markedly inhibited and strong hyperpolarization was induced by the presence of 10 nM or 100 nM PACAP (Fig. 2C and D). Under control conditions, the resting membrane potential and frequency generated by colonic ICC were recorded as -51.4±1.2 mV and 10.6±0.9 cycles/5 min, respectively (n=18, Fig. 2E and F). When ICC were treated with high concentrations of PACAP, the resting membrane potentials were measured as -57.8±1.7 mV at 10 nM (n=4) and -61.7±3.02 mV at 100 nM (n=5). The mean values of pacemaker potential frequencies were changed to 0.2±0.1 cycles/5 min at 10 nM and 0.1±0.19 cycles/5 min at 100 nM by addition of high dose PACAP (Fig. 2E and F).


Pituitary Adenylate Cyclase-activating Polypeptide Inhibits Pacemaker Activity of Colonic Interstitial Cells of Cajal.

Wu MJ, Kee KH, Na J, Kim SW, Bae Y, Shin DH, Choi S, Jun JY, Jeong HS, Park JS - Korean J. Physiol. Pharmacol. (2015)

Effects of various concentrations of pituitary adenylate cyclase-activating peptide (PACAP) on pacemaker potentials recorded in cultured interstitial cells of Cajal (ICC) from mouse colon. (A), (B), (C), and (D) show pacemaker potentials of ICC exposed to PACAP (0.1 nM, 1 nM, 10 nM, or 100 nM) under current-clamp mode (I=0). Vertical solid lines represent the amplitude of pacemaker potentials and horizontal solid lines represent the duration of recording (s) of pacemaker potentials. The dotted lines indicate the resting membrane potential. (E) and (F) summarize the effects of PACAP on pacemaker potentials in ICC. Bars represent the means±SE. *Asterisks indicate a statistically significant difference from controls (p<0.05). Con, control.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4553403&req=5

Figure 2: Effects of various concentrations of pituitary adenylate cyclase-activating peptide (PACAP) on pacemaker potentials recorded in cultured interstitial cells of Cajal (ICC) from mouse colon. (A), (B), (C), and (D) show pacemaker potentials of ICC exposed to PACAP (0.1 nM, 1 nM, 10 nM, or 100 nM) under current-clamp mode (I=0). Vertical solid lines represent the amplitude of pacemaker potentials and horizontal solid lines represent the duration of recording (s) of pacemaker potentials. The dotted lines indicate the resting membrane potential. (E) and (F) summarize the effects of PACAP on pacemaker potentials in ICC. Bars represent the means±SE. *Asterisks indicate a statistically significant difference from controls (p<0.05). Con, control.
Mentions: We examined whether exogenous exposure to PACAP triggered dose-dependent effects on ICC pacemaker potentials in current-clamp mode (I=0). Under a current clamp, ICC generated spontaneous pacemaker potentials. The application of 0.1 nM or 1 nM PACAP induced slight hyperpolarization with reduction of frequency (Fig. 2A and B). Next, we found that pacemaker potentials were markedly inhibited and strong hyperpolarization was induced by the presence of 10 nM or 100 nM PACAP (Fig. 2C and D). Under control conditions, the resting membrane potential and frequency generated by colonic ICC were recorded as -51.4±1.2 mV and 10.6±0.9 cycles/5 min, respectively (n=18, Fig. 2E and F). When ICC were treated with high concentrations of PACAP, the resting membrane potentials were measured as -57.8±1.7 mV at 10 nM (n=4) and -61.7±3.02 mV at 100 nM (n=5). The mean values of pacemaker potential frequencies were changed to 0.2±0.1 cycles/5 min at 10 nM and 0.1±0.19 cycles/5 min at 100 nM by addition of high dose PACAP (Fig. 2E and F).

Bottom Line: The effects of SQ-22536 on pacemaker potential frequency and membrane hyperpolarization were rescued by co-treatment with glibenclamide (an ATP-sensitive K(+) channel blocker).However, neither N (G)-nitro-L-arginine methyl ester (L-NAME, a competitive inhibitor of NO synthase) nor 1H-[1,2,4]oxadiazolo[4,3-α]quinoxalin-1-one (ODQ, an inhibitor of guanylate cyclase) had any effect on PACAP-induced activity.These results provide evidence of a physiological role for PACAP in regulating gastrointestinal (GI) motility through the modulation of ICC activity.

View Article: PubMed Central - PubMed

Affiliation: Department of Physiology, Chonnam National University Medical School, Gwangju 501-757, Korea.

ABSTRACT
This study aimed to investigate the effect of pituitary adenylate cyclase-activating peptide (PACAP) on the pacemaker activity of interstitial cells of Cajal (ICC) in mouse colon and to identify the underlying mechanisms of PACAP action. Spontaneous pacemaker activity of colonic ICC and the effects of PACAP were studied using electrophysiological recordings. Exogenously applied PACAP induced hyperpolarization of the cell membrane and inhibited pacemaker frequency in a dose-dependent manner (from 0.1 nM to 100 nM). To investigate cyclic AMP (cAMP) involvement in the effects of PACAP on ICC, SQ-22536 (an inhibitor of adenylate cyclase) and cell-permeable 8-bromo-cAMP were used. SQ-22536 decreased the frequency of pacemaker potentials, and cell-permeable 8-bromo-cAMP increased the frequency of pacemaker potentials. The effects of SQ-22536 on pacemaker potential frequency and membrane hyperpolarization were rescued by co-treatment with glibenclamide (an ATP-sensitive K(+) channel blocker). However, neither N (G)-nitro-L-arginine methyl ester (L-NAME, a competitive inhibitor of NO synthase) nor 1H-[1,2,4]oxadiazolo[4,3-α]quinoxalin-1-one (ODQ, an inhibitor of guanylate cyclase) had any effect on PACAP-induced activity. In conclusion, this study describes the effects of PACAP on ICC in the mouse colon. PACAP inhibited the pacemaker activity of ICC by acting through ATP-sensitive K(+) channels. These results provide evidence of a physiological role for PACAP in regulating gastrointestinal (GI) motility through the modulation of ICC activity.

No MeSH data available.