Locality-dependent descending reflex motor activity in the anal canal--cholinergic and nitrergic contributions in the rat model.
OBJECTIVE
Since the distal part of the intestine is targeted by a wide range of pathogens, the motility of the recto-anal region has been the object of many experimental and clinical observations. In this study, we investigated descending motor responses in the anal canal as a measure of the activation of autonomic reflex pathways underlying evacuatory recto-anal activity.


METHODS
The partitioned organ bath method was used to register motor responses of the anal canal as induced by balloon distension of the rectum in isolated rat recto-anal preparations.


RESULTS
Distension-induced descending responses of the anal canal comprised contractions (with distension at a distance of 15 mm), initial contractions and secondary relaxations (at 10 mm) and short contractions followed by deep relaxations (at 3-5 mm). Decreasing the distance between the distension stimulus and the anal canal resulted in a decreased contraction response and increased relaxation. Tetrodotoxin (0.1 micromol/L) inhibited these responses. Atropine (0.3 micromol/L) decreased contraction and did not change the relaxation response. N(G)-nitro-L-arginine (0.5 mmol/L) enhanced contraction in both the absence and presence of atropine. L-arginine (0.5 mmol/L) inhibited contraction and extended relaxation in atropine-pretreated preparations. The actions of N(G)-nitro-L-arginine and L-arginine were more pronounced in the aboral direction. ChAT-positive nerve fibers were observed in myenteric ganglia of the rectum and the anal canal. The density of NADPH-diaphorase-positive neurons was higher in the anal canal region.


CONCLUSIONS
Our results suggest that locality-dependent activation of the descending reflex neuromuscular communications underlie evacuatory activity in the recto-anal region. This activation response involves long excitatory cholinergic and non-cholinergic pathways along the rectum and short inhibitory nitrergic pathways located predominantly in the anal canal region.
Radomirov
Radomir
R
Institute of Neurobiology, Bulgarian Academy of Sciences, 1113 Sofia, Bulgaria. radomir@bio.bas.bg
Ivancheva
Christina
C
Itzev
Dimitar
D
Petkova-Kirova
Polina
P
D001003:Anal Canal / Q000187:drug effects* / Q000502:physiology; D000818:Animals; D001120:Arginine / Q000494:pharmacology; D001285:Atropine / Q000494:pharmacology; D018678:Cholinergic Agents / Q000494:pharmacology*; D002799:Cholinergic Fibers / Q000187:drug effects; D005769:Gastrointestinal Motility / Q000187:drug effects* / Q000502:physiology; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D026602:Nitrergic Neurons / Q000187:drug effects; D019335:Nitroarginine / Q000494:pharmacology; D009924:Organ Culture Techniques; D010276:Parasympatholytics / Q000494:pharmacology; D051381:Rats; D026941:Sodium Channel Blockers / Q000494:pharmacology; D013779:Tetrodotoxin / Q000494:pharmacology
D018678:Cholinergic Agents; D010276:Parasympatholytics; D026941:Sodium Channel Blockers; D019335:Nitroarginine; D013779:Tetrodotoxin; D001285:Atropine; D001120:Arginine
Auton Neurosci. 2004 Mar 31;111(1):48-56
15109938
Gastroenterology. 1990 Oct;99(4):1008-15
2394323
Eur J Pharmacol. 1988 Mar 22;148(1):43-9
2454831
Trends Neurosci. 2001 Apr;24(4):211-5
11250004
Am J Physiol Gastrointest Liver Physiol. 2002 Jul;283(1):G148-56
12065302
Am J Physiol Gastrointest Liver Physiol. 2005 Sep;289(3):G397-406
15933221
Dis Colon Rectum. 2004 Feb;47(2):210-8
15043292
J Pharmacol Exp Ther. 1993 Jan;264(1):391-6
7678649
Am J Physiol Gastrointest Liver Physiol. 2002 Aug;283(2):G384-9
12121886
Neurogastroenterol Motil. 2006 Jul;18(7):507-19
16771766
Aliment Pharmacol Ther. 2001 Jul;15(7):887-98
11421863
Am J Physiol Gastrointest Liver Physiol. 2002 Mar;282(3):G443-9
11841994
Gastroenterology. 2005 Dec;129(6):1954-66
16344064
Int J Colorectal Dis. 2007 Nov;22(11):1319-24
17569063
Methods Find Exp Clin Pharmacol. 2001 Jun;23(5):223-9
11712640
Zhonghua Wei Chang Wai Ke Za Zhi. 2006 Nov;9(6):538-41
17143805
J Smooth Muscle Res. 2003 Apr;39(1-2):11-20
12889852
Pharmacol Rev. 2000 Mar;52(1):63-89
10699155
Dis Colon Rectum. 1998 Feb;41(2):200-8
9556245
Br J Surg. 1996 Apr;83(4):493-8
8665237
Annu Rev Physiol. 1995;57:659-82
7539992
Am J Physiol. 1986 Jul;251(1 Pt 1):G40-5
3014895
J Neurosci Methods. 1983 Nov;9(3):229-34
6363828
Methods Find Exp Clin Pharmacol. 2008 Apr;30(3):201-7
18597004
World J Gastroenterol. 2006 Jul 28;12(28):4549-52
16874870
J Histochem Cytochem. 1981 Apr;29(4):577-80
6166661
J Physiol. 2005 Apr 15;564(Pt 2):589-601
15718264
Am J Physiol Gastrointest Liver Physiol. 2005 Aug;289(2):G351-60
15817810
Neurochem Int. 2007 Oct;51(5):289-96
17707950
Am J Physiol Gastrointest Liver Physiol. 2004 Nov;287(5):G1017-27
15256359
Neurochem Int. 2008 Mar-Apr;52(4-5):834-45
18022291
Br J Pharmacol. 1996 Jun;118(4):973-83
8799571
Dis Colon Rectum. 1995 Sep;38(9):916-20
7656737
Am J Gastroenterol. 2000 Mar;95(3):715-9
10710063
J Spinal Cord Med. 2003 Winter;26(4):380-3
14992340
Neurogastroenterol Motil. 1998 Jun;10(3):219-25
9659665
Brain Res Bull. 2009 Apr 29;79(2):147-55
19195494
Gut. 2005 Aug;54(8):1107-13
16009682
J Physiol. 1998 Nov 1;512 ( Pt 3):893-906
9769430