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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 pituitary adenylate cyclase-activating peptide (PACAP) on pacemaker currents recorded in cultured interstitial cells of Cajal (ICC) from mouse colon. (A) shows the pacemaker currents of ICC exposed to PACAP (1 nM) in voltage-clamp mode at -70 mV holding potentials. PACAP inhibited the amplitude and frequency of pacemaker currents in ICC. The dotted lines indicate the control resting current levels. Responses to PACAP are summarized in (B) and (C). Bars represent the means±SE. *Asterisks indicate a statistically significant difference from controls (p<0.05).
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Figure 1: Effects of pituitary adenylate cyclase-activating peptide (PACAP) on pacemaker currents recorded in cultured interstitial cells of Cajal (ICC) from mouse colon. (A) shows the pacemaker currents of ICC exposed to PACAP (1 nM) in voltage-clamp mode at -70 mV holding potentials. PACAP inhibited the amplitude and frequency of pacemaker currents in ICC. The dotted lines indicate the control resting current levels. Responses to PACAP are summarized in (B) and (C). Bars represent the means±SE. *Asterisks indicate a statistically significant difference from controls (p<0.05).

Mentions: ICC cultured from mouse colon were identified with Kit immunofluorescence. Kit-positive cells had a distinctive morphology that was easily recognized in cultures. We used electrophysiological assays to determine the effect of PACAP on ICC. Electrophysiological recordings were performed from cultured colonic ICC under voltage-clamp mode at -70 mV. Under control conditions, ICC showed spontaneous pacemaker currents. The frequency and amplitude recorded from colonic ICC were measured as 11.6±1.8 cycles/5 min and 722.4±91.09 pA (n=5), respectively, under physiological conditions (Fig. 1B and C). Administration of PACAP (1 nM) to the bath solution slightly showed outward currents and inhibited pacemaker activity (Fig. 1A). The frequency and amplitude values of pacemaker currents under voltage-clamp mode in the presence of PACAP (1 nM) were significantly different from control values (n=5, Fig. 1B and C).


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 pituitary adenylate cyclase-activating peptide (PACAP) on pacemaker currents recorded in cultured interstitial cells of Cajal (ICC) from mouse colon. (A) shows the pacemaker currents of ICC exposed to PACAP (1 nM) in voltage-clamp mode at -70 mV holding potentials. PACAP inhibited the amplitude and frequency of pacemaker currents in ICC. The dotted lines indicate the control resting current levels. Responses to PACAP are summarized in (B) and (C). Bars represent the means±SE. *Asterisks indicate a statistically significant difference from controls (p<0.05).
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 1: Effects of pituitary adenylate cyclase-activating peptide (PACAP) on pacemaker currents recorded in cultured interstitial cells of Cajal (ICC) from mouse colon. (A) shows the pacemaker currents of ICC exposed to PACAP (1 nM) in voltage-clamp mode at -70 mV holding potentials. PACAP inhibited the amplitude and frequency of pacemaker currents in ICC. The dotted lines indicate the control resting current levels. Responses to PACAP are summarized in (B) and (C). Bars represent the means±SE. *Asterisks indicate a statistically significant difference from controls (p<0.05).
Mentions: ICC cultured from mouse colon were identified with Kit immunofluorescence. Kit-positive cells had a distinctive morphology that was easily recognized in cultures. We used electrophysiological assays to determine the effect of PACAP on ICC. Electrophysiological recordings were performed from cultured colonic ICC under voltage-clamp mode at -70 mV. Under control conditions, ICC showed spontaneous pacemaker currents. The frequency and amplitude recorded from colonic ICC were measured as 11.6±1.8 cycles/5 min and 722.4±91.09 pA (n=5), respectively, under physiological conditions (Fig. 1B and C). Administration of PACAP (1 nM) to the bath solution slightly showed outward currents and inhibited pacemaker activity (Fig. 1A). The frequency and amplitude values of pacemaker currents under voltage-clamp mode in the presence of PACAP (1 nM) were significantly different from control values (n=5, Fig. 1B and C).

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.