ABSTRACT
Participation of nitric oxide, vasoactive intestinal peptide (VIP) and pituitary adenylate cyclase activating peptide (PACAP) in nonadrenergic, noncholinergic (NANC) relaxation of longitudinal muscle of various intestinal regions in Sprague Dawley rats (8-week-old) was studied in vitro. Nitric oxide was suggested to participate in NANC relaxation of every intestinal region studied. But the participation was partial and its extent varied among the regions: significant in the proximal colon and rectum, and moderate in the jejunum, ileum and distal colon. Participation of PACAP in NANC relaxation was suggested only in the distal colon, while that of VIP was not detected in any of regions. Results obtained in the present study indicate that extent of participation of nitric oxide in NANC relaxation in Sprague Dawley rat intestine is more significant than those of other strains, Wistar and Wistar-ST.
Subject(s)
Gastrointestinal Motility/physiology , Muscle Contraction/physiology , Muscle Relaxation/physiology , Rats, Sprague-Dawley/physiology , Animals , Atropine/pharmacology , Colon/drug effects , Enzyme Inhibitors/pharmacology , Gastrointestinal Motility/drug effects , Guanethidine/pharmacology , Ileum/drug effects , Jejunum/drug effects , Muscle Relaxation/drug effects , Neuropeptides/physiology , Nitric Oxide/physiology , Nitroarginine/pharmacology , Peptide Fragments/pharmacology , Pituitary Adenylate Cyclase-Activating Polypeptide , Rats , Rats, Wistar/physiology , Species Specificity , Vasoactive Intestinal Peptide/pharmacology , Vasoactive Intestinal Peptide/physiologyABSTRACT
Participation of the nitric oxide-cyclic GMP pathway in nonadrenergic, noncholinergic (NANC) relaxation induced by electrical field stimulation of longitudinal muscle of the rectum of Wistar-ST rats was studied by using a selective inhibitor of soluble guanylyl cyclase, 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ). ODQ concentration dependently inhibited the relaxation and at 10 microM, maximally inhibited it by 83%. However, results obtained with N(G)-nitro-L-arginine, L-arginine and exogenously added nitric oxide excluded the participation of nitric oxide in the relaxation. An inhibitor of cyclic GMP-dependent protein kinase (PKG) partially (39%) inhibited the relaxation. ODQ also significantly inhibited the relaxation, which persisted after the PKG inhibitor-treatment, by 85%. The results strongly suggest that ODQ inhibits the NANC relaxation in a cyclic GMP-PKG pathway-independent manner.
Subject(s)
Cyclic GMP-Dependent Protein Kinases/physiology , Cyclic GMP/physiology , Enzyme Inhibitors/pharmacology , Guanylate Cyclase/antagonists & inhibitors , Muscle Relaxation/drug effects , Oxadiazoles/pharmacology , Quinoxalines/pharmacology , Rectum/drug effects , Animals , In Vitro Techniques , Male , Neuropeptides/pharmacology , Nitroarginine/pharmacology , Peptide Fragments/pharmacology , Pituitary Adenylate Cyclase-Activating Polypeptide , Rats , Rats, Wistar , Rectum/physiology , Vasoactive Intestinal Peptide/pharmacologyABSTRACT
Participation of nitric oxide and vasoactive intestinal peptide (VIP) in electrical field stimulation-induced nonadrenergic, noncholinergic (NANC) relaxation of longitudinal muscle and in balloon distension-induced descending NANC relaxation of circular muscle were studied in the distal colon of Wistar-ST and Sprague-Dawley rats. The extent of the nitric oxide-mediated component was approximately 50% in longitudinal and circular muscle of Sprague-Dawley rats, whereas this component was absent in both muscles of Wistar-ST rats. The extent of the VIP-mediated component was approximately 40% in longitudinal muscle of Wistar-ST rats and circular muscle of Sprague-Dawley rats, whereas this component was absent in circular muscle of Wistar-ST rats and longitudinal muscle of Sprague-Dawley rats. In circular muscle of Sprague-Dawley rats, in which participation of both nitric oxide and VIP in the relaxation was suggested, inhibition of descending relaxation by N(G)-nitro-L-arginine (L-NOARG) together with VIP-(10-28) was similar to that by either of the antagonists, and exogenous VIP-induced relaxation was not affected by L-NOARG, but exogenous nitric oxide-induced relaxation was partly inhibited by VIP-(10-28). These results suggest a linkage of the pathways mediated by nitric oxide and VIP. In the immunohistochemical studies, nitric oxide synthase or VIP immunoreactive neurons were seen in the ganglia, primary internodal strands of the myenteric plexus and in the circular muscle layer. However, the overall appearance of immunoreactive cell bodies in the myenteric plexus and the numbers of immunoreactive fibers in the circular muscle layer appeared to be similar in Wistar-ST and Sprague-Dawley rats. These results suggest that mediators of NANC relaxation in the distal colon are different in different strains of rats, i.e., Wistar-ST and Sprague-Dawley, although no such difference was seen in immunohistochemical studies.
Subject(s)
Autonomic Nervous System/physiology , Colon/innervation , Norepinephrine/physiology , Animals , Antibody Specificity , Charybdotoxin/pharmacology , Colon/physiology , Electric Stimulation , Enzyme Inhibitors/pharmacology , Immunohistochemistry , Male , Microscopy, Fluorescence , Muscle Relaxation/drug effects , Nerve Tissue Proteins/metabolism , Nitric Oxide Synthase/antagonists & inhibitors , Nitric Oxide Synthase/metabolism , Nitric Oxide Synthase Type I , Nitroarginine/pharmacology , Rats , Rats, Sprague-Dawley , Rats, Wistar , Receptors, Vasoactive Intestinal Peptide/antagonists & inhibitors , Species Specificity , Vasoactive Intestinal Peptide/metabolismABSTRACT
Mediators of nonadrenergic, noncholinergic (NANC) relaxation in longitudinal muscle of several regions of ICR mouse intestine were studied. An inhibitor of synthesis of nitric oxide, N(G)-nitro-L-arginine (L-NOARG) at 10 microM significantly inhibited NANC relaxations induced by electrical field stimulation (EFS) in the jejunum, ileum, and the proximal and distal colon. Especially in the ileum extent of the inhibition was more than 80%. An antagonist of vasoactive intestinal peptide (VIP) receptors, VIP(10-28) at 3 microM partially inhibited the EFS induced relaxations in the jejunum and proximal colon, but very slightly in the distal colon and had no effect in the ileum. An antagonist of pituitary adenylate cyclase activating peptide (PACAP) receptor, PACAP(6-38) at 3 microM partially inhibited the EFS-induced relaxations in the proximal and distal colon, but not in the jejunum and ileum. Totals of the percentages of relaxant components mediated by nitric oxide, VIP and PACAP in every region are roughly equal to a hundred percent. In another series of experiments, EFS-induced relaxations were almost completely inhibited by the treatment of the segments with L-NOARG and VIP(10-28) in the jejunum, with L-NOARG, VIP(10-28) and PACAP(6-38) in the proximal colon, and with L NOARG and PACAP(6-38) in the distal colon. The present results suggest that nitric oxide solely mediates the relaxation of longitudinal muscle of the ileum of ICR mice, whereas nitric oxide and VIP co-mediate it in the jejunum, nitric oxide, VIP and PACAP in the proximal colon, and nitric oxide and PACAP in the distal colon.
Subject(s)
Intestines/physiology , Muscle Relaxation/physiology , Muscle, Smooth/physiology , Animals , Colon/chemistry , Colon/innervation , Colon/physiology , Electric Stimulation , Electrophysiology , Enzyme Inhibitors/pharmacology , Ileum/chemistry , Ileum/innervation , Ileum/physiology , Intestines/chemistry , Intestines/innervation , Jejunum/chemistry , Jejunum/innervation , Jejunum/physiology , Male , Mice , Mice, Inbred ICR , Muscle Relaxation/drug effects , Muscle, Smooth/innervation , Neuropeptides/antagonists & inhibitors , Neuropeptides/metabolism , Nitric Oxide/metabolism , Nitroarginine/pharmacology , Pituitary Adenylate Cyclase-Activating Polypeptide , Receptors, Adrenergic , Receptors, Cholinergic , Receptors, Pituitary Adenylate Cyclase-Activating Polypeptide , Receptors, Pituitary Hormone/physiology , Receptors, Vasoactive Intestinal Peptide/physiology , Vasoactive Intestinal Peptide/antagonists & inhibitors , Vasoactive Intestinal Peptide/metabolismABSTRACT
Participation of nitric oxide in the electrical field stimulation-induced nonadrenergic, noncholinergic (NANC) relaxation in various intestinal regions was studied in 2- to 50-week-old Wistar rats. In the jejunum of 2-week-old rats, the extent of the nitric oxide-mediated component of the relaxation of longitudinal muscle was approximately 60-70%, whereas the component was 40-50% in 4-week-old rats and was absent in 8- and 50-week-old rats. Thus, nitric oxide seems to be the most important mediator at young ages but its significance is lost with age. The same tendency as that in the jejunum was also shown in longitudinal muscle of the ileum, proximal and distal colon, and rectum. The tendency was also shown in the circular muscle of the rectum. Sensitivity of the longitudinal muscle of the jejunum and proximal colon to exogenously added nitric oxide was high in younger rats. Immunoreactive structures for nitric oxide synthase were observed in the circular muscle layer of the rectum. The population of the structures was denser in 4-week-old than that in 50-week-old. The results suggest that NANC relaxation in every region of the intestine at 2-week-old is almost solely mediated by nitric oxide, and its significance as an inhibitory mediator gradually or rapidly decreases with age.
