Ganong, W.F. () Review of Medical Physiology. 22nd Edition, McGraw-Hill Medical, New York. a LANGE medical book. Ganong’s. Review of. Medical Physiology. Twenty-Third Edition. New York Chicago San Francisco Lisbon London Madrid Mexico City. Ganong’s Review of Medical Physiology, 22nd Edition (Lange Basic Science). Ganong’s Review of Medical Physiology, 22nd Edition (Lange Basic Science).
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Appendicitis poses a great health problem worldwide. Previous studies demonstrated structural damage to neuronal network and interstitial cell of Cajal in appendicitis.
But the mechanisms involved in mediating the contractility in inflamed vermiform appendix is not known till date.
The present in vitro study was performed to find out the mechanisms responsible for contractility in the inflamed human vermiform appendix. Control contractions were recorded for 30 min after an initial tension of 0. Initially dose-response experiments of agonists acetylcholine, serotonin and histamine were performed separately 2n2d the dose that produced maximum contraction was determined with each agonist.
William Francis Ganong
This maximal dose of agonist was used to elicit contractions in next series of experiments before and after pre-treatment with appropriate antagonists like atropine, ondansetron 5-HT 3 antagonist and chlorpheniramine maleate respectively.
Histamine produced very low amplitude of contractions in comparison to ACh or 5-HT and did not exhibit dose-response relations. The observations suggested that the contractility of longitudinal muscle strips of inflamed vermiform appendix in human beings was predominantly mediated by muscarinic and serotonergic 5-HT 3 mechanisms, whereas, histaminergic mechanisms played a minor role in mediating the contractility.
Inflammation of the appendix is a common cause of abdominal pain especially in adolescents and young adults that often requires surgical treatment. Most of the observations available on appendix till date in human beings and animals were focused on histopathology and immunohistochemistry. In the previous histopathological observations, authors reported significant ultrastructural damage of neurons and interstitial cell of Cajal networks in appendicitis [ 34 ].
In our earlier observations, we reported mechanisms involved in contractility of longitudinal muscle strips of normal human vermiform appendix involving muscarinic and serotonergic mechanisms [ 5 ]. Beside, structural changes in the muscle of appendix, variety of inflammatory agents like Prostaglandins PGshistamine, kinins etc. But till date, there are no reports available that demonstrate the mechanisms mediating the contractility of appendix in inflamed state.
Therefore, the present in vitro study was undertaken to investigate the underlying mechanisms involved in mediating the contractility of longitudinal muscle strips of inflamed vermiform appendix of human beings, using ACh, 5-HT and histamine as chemical transmitters. The present in vitro experimental study on human vermiform appendix was conducted in the period between May to October But, only those specimens of appendices were included in the study which was diagnosed as appendicitis on microscopy.
Gangrenous, perforated, tumourous appendices were excluded from the study by naked eye examination done by operating surgeon in the operation theatre. Specimen resected by means of laparoscopic surgery was also excluded.
In the current study, 24 samples of human inflamed vermiform appendix were recruited as per the inclusion criteria. Appendices were cut in two halves, proximal half and distal half in the operation theater. Thereafter, the bottle with sample was carried to the Department of Physiology, Institute of Medical Sciences, Banaras Hindu University for contractility study.
The distal half of the appendix sample was transported to Department of Pathology, Institute of Medical Sciences, Banaras Hindu University for confirmation of diagnosis of appendicitis by microscopy.
These three strips were used to test three different agonist ACh, 5-HT and histamine. The methodology used to record the muscle contractions was followed as per previous reports [ 7 ]. In brief, one end of the muscle strip was tied to a glass tube via a thread and a piece of thread was also tied to other end of the muscle strip.
The tissue was allowed to stabilise for 30 minutes under an initial tension of 0. In the present study, experiments were divided into three groups, one for each agonist ACh, 5-HT and histamine.
Then, each group was subdivided into two subgroups subgroup 1 and subgroup 2. In subgroup 1 of each group, dose-response experiments of agonist were performed to determine dose of agonist that elicited maximum amplitude of contraction.
In subgroup 2 of each group, the agonist induced muscle contractions were obtained before and after pretreatment with appropriate antagonist atropine, ondansetron and chlorpheniramine maleate. In Group 1, subgroup 1 set of experiments, after initial stabilisation of the muscle strip for 30 minutes, different doses of ACh in increasing order 0. In between two doses, the muscle strip was washed twice at an interval of 10 minutes with Krebs-Ringer solution and allowed to stabilise for another 10 minutes before recording muscle contractions with next higher dose of ACh.
In subgroup 1 set of experiments of Group 2 and 3, the dose response of 5-HT 0. Protocols followed for subgroup 2 set of experiments of Group 2 and 3 were similar to experimental protocol of subgroup 2 set of experiments of Group 1. Then, the muscle strip was soaked on the blotting paper for 10 seconds. Its weight was obtained on an electronic weighing machine. The stock solutions of 10 mM concentration of each agonists and antagonists were prepared in distilled water and were kept in refrigerator.
During experiment, stock solutions were diluted to appropriate concentration with Krebs-Ringer solution.
Analytical grade chemicals were used in the present study. GraphPad Prism 6 was used for statistical analysis.
Data analysis of the dose-response was performed using One-Way Analysis Of Variance ANOVA and Students t-test for paired observations was used to compare between two groups agonist induced contractions before and after exposure to antagonist. Contractions elicited in the longitudinal muscle strips of inflamed vermiform appendix by ACh 0.
Further, histamine did not demonstrate any dose dependent relation in the muscle contractions. Further, the amplitude of contractions produced by histamine 0. In the present in vitro study, longitudinal muscle strips of inflamed vermiform appendix demonstrated contractile responses to ACh, 5-HT and histamine. Pre-exposure of the muscle strips to atropine significantly blocked ACh elicited responses. Pretreatment with ondansetron completely blocked the 5-HT induced contractile responses.
Further, histamine induced contractions were of small amplitude but they were blocked by prior application with CPM. In the present study, dose-dependent increase in the amplitude of contractions of inflamed appendix observed with ACh 0. This may be due to either upregulation of receptors or participation of more and more receptors [ 8 ]. Vermiform appendix contains enteric nervous system as it is present in the other parts of gastrointestinal tissues.
Further extrinsically, myentric plexus is supplied by parasympathetic fibres of vagus nerve [ 6 ]. Previous studies demonstrated blockade of electrically stimulated contractions of normal appendix by prior exposure of muscle tissue to atropine, suggesting, cholinergic involvement [ 1112 ]. Further, studies also reported the involvement of muscarinic receptors in mediating the ACh induced contractility in the smooth muscles of gut and normal appendix [ 513 ].
Thus, findings suggest the role of cholinergic-muscarinic mechanisms physiopogy mediating the contractility in inflamed appendix. However, ACh induced contractions were not completely blocked by atropine as observed in the present study. Earlier studies reported the existence of multiple types of interneurons in the enteric nervous system of the gut which receive their innervations by parasympathetic fibers of vagus nerve. Cholinergic activation of these neurons releases variety of neurotransmitters and amines like 5-HT which mediate contractions in the smooth muscles of gut [ 5614 ].
Thus, these observations also indicate the role of pathways other than muscarinic for mediating ACh induced contractions in inflamed appendix. Reports suggested meddical 5-HT mediated its contractile effect in the gastrointestinal system either directly or via myenteric neuronal network [ 56 ].
Ondansetron has been classified as 5-HT 3 blocker [ 16 ]. Thus, the findings suggest the involvement of 5-HT 3 pathways in mediating the contractility of the inflamed appendix. Similar observations of histamine are reported in other gut tissue like stomach, colon and 22hd in normal appendix [ 1718 ]. CPM is a known H 1 – receptor blocker and feview mediates contractions of the smooth muscles by activating phospholipase-C in the intestine [ 6 ].
Thus, findings suggest the role of H 1 – receptors in mediating the histamine induced contractility of inflamed appendix. In addition, amplitude of histamine 0. Above observations suggest the participation of very low population of H 1 -receptors in contractility of inflamed appendix muscle. Thus, findings suggest the minor contribution of histamine in mediating the contractility of inflamed physillogy. Comparison of contractility of normal and inflamed appendix.
The data of normal appendix is derived from our earlier observation [ 5 ]. Decreased contractility have been reported in other parts of the intestine where any injury that leads to inflammation reduces the motility of the intestine [ 1920 ]. Injury or inflammation has been reported to cause ultrastructural damage to the myenteric neurons [ 34 ]. Further, varieties of chemicals are released in inflammation.
The chemical injury may cause denaturation of receptors and contractile proteins of muscles [ 20 ]. Hence, diminution in quantity and quality of receptors or contractile proteins may lead to significant decrease in magnitude of contractions of longitudinal muscles of inflamed appendix as observed in the study.
These substances produce smooth muscle relaxation [ 6 ]. Thus, above explanation may be the additional pathway which may produce significant diminution in the magnitude of contraction in inflamed appendix muscle as observed in the study. A 5-HT is a mediator released in inflammatory conditions [ 21 ]. Thus, the failure of 5-HT to increase the contractility in the inflamed appendix points toward the pathology lying in the muscle itself.
Ganong’s Review of Medical Physiology, 25e | AccessMedicine | McGraw-Hill Medical
However, increase in blockade by atropine demonstrates enhanced role for cholinergic-muscarinic mechanisms in inflamed appendix. Comparison of effect of antagonist on muscle contractility of normal and inflamed appendix.
Thus, experiments are required in future to investigate the role of other chemical agents which could enrich the pathophysiology of contractility of inflamed appendix. An important limitation of the study was related to the use of physiograph instead of computerised data acquisition system which could have also recorded the frequency of contractions along with the amplitude of contractions.
The present study was performed on longitudinal muscles in in vitro situations. Hence, this study did not provide information that could explain the contractility of the circular muscles of the inflamed appendix.
Further, reservations are there to extrapolate editikn present in vitro findings with in vivo situations of inflamed appendix. However, the positive aspect of the study was that it enhanced the basic pool of knowledge about appendicitis.
The findings suggested that the contractility of the longitudinal muscle strips of inflamed vermiform appendix is decreased editoin comparison to normal appendix and it is mediated pre-dominantly via cholinergic-muscarinic and serotonergic 5-HT 3 mechanisms. Histaminergic H 1 mechanism plays minor role in mediating the contractility in inflamed appendix. We thank all the patients and their relatives for their participation and giving their consent for the present study.
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