The simulated experiment of the practical is about the addition of agonists and antagonists on a guinea pig ileum and observing the effect of these agonists and antagonists on the ileum. This experiment is carried out with an aim to determine the effects of different concentrations of agonists and antagonists on the ileum of a guinea pig. In this experiment the type of data that are to be collected include the traces of acetycholine in the guinea pig ileum on addition of different concentrations of matropine. The expected values of the experiment are that the contraction of the ileum to change depending on the concentrations of the acetylcholine added and also according to the concentration of the matropine added. The results can therefore be used to determine the effects of both Matropine and Acetylcholine in smooth tissue, which in this case the smooth tissue is the ileum of a guinea pig.
After setting up the bath, the Chaemograph is then set. It has a nob at the top, which controls the movement of its drum. On this drum a tracing paper has been placed or mounted. The power button of the Chaemograph is then turned on. The speed of rotation of the drum, is controlled by the speed rotation switch, which can be moved from left to right or right to left till the desired speed of the drum is achieved. The speed in this experiment was in metres per minute. The ileum of the guinea pig to be used, is then places in the inner bath of the pharmacological solution and the experiment is then started as the set up is ready for use. The type of smooth muscle that is responsible for contractions in the guinea pig is the ileum. This can be compared to other smooth muscles such as Aorta in the case of rats and such like animals. This experiment was as an a simulated one and similar experiments have been done on other similar creatures with soft tissues.
Graphs have been drawn to show dose-response curves and tables used to present the data collected from the experiment. Charts have also been prepared as part of the presentation.
Histamine Agonist: More Study on the Experiment
Cholinergic neurotransmission is a type of neurotransmission that pertains the nerve fibres, which are responsible in the liberation of acetylcholine, which comes out of the myoneural junctions. There are a number of agonists and antagonists to cholinergic neurotransmissions. One of the most common agonists in the case of the guinea pig is the Histamine-H3 agonist.
Histamine causes an inhibition that depends on a dose. The inhibition is of a contraction of a guinea pig tracheal tube preparation, which is vagally mediated. The inhibition however does not change the contraction in the tracheal system which is inducred by acetycholine applied exogenously. The blockade of the histamine receptors H1- and H2- and the adrenoceptors leads to the prevention of the inhibitory effect of methylhistamine. On the other hand, the specific H3-antagonist thioperamide prevents the effect of methylhistamine on the contraction of the trachea. When receptor antogonists are present, histamine also tend to inhibit tracheal contractions which are vagally mediated. Methylistamine has an inhibitory effect which is greater with vagus nereve stimulation than with stimulation which is postganglionic and comes with stimulation fromm electric field. This suggests that the H3-receptors become localized to both the cholinergic ganglia and similarly in the post-ganglionic endings of the nerve. From the results, the H3-receptors are found in the vagus nerves and these nerves are known to modulate the cholinergic neurotransmission, the process occurring in the airways.
Histamine as an agonist has some effects in relation to the diseases that it is to treat. Histamine is an acid reducer and can either be taken by mouth or injected into the body system. They are administered to control not only daytime symptoms but also nighttime symptoms. Histamine just like any other drugs has side effects and these effects should be addressed to the patients by their doctors in time, so they know a symptom when they see one.
Discussion of Results from the Experiment
Acetylcholine on the other hand is also a chemical messenger and also a neurotransmitter and controls contraction of skeletal and voluntary muscles. On smooth muscle, acetylcholine will activate a different kind of receptor that is the muscarinic receptor. This receptor binds the acetylcholine. Acetylcholine has two common effects depending on its concentration. At high concentrations the acetylcholine causes endothelium-dependent relaxation and a contraction, which is endothelium-independent. At low concentrations however, the acetylcholine causes a relaxation and hyper polarization which are persistent and endothelium independent.
Atropine and Acetylcholine both have effects on the contraction and relaxation of smooth muscles. The amount of contraction or relaxation on smooth muscles when Atropine or Acetylcholine is added depends on the concentrations and amount of the Atropine or Acetylcholine added respectively. In conclusion, the experiment was a success as the objective was achieved.
British Journal of Pharmacology. The action of acetylcholine and other drugs on the efflux of potassium and rubidium from smooth muscle of a guinea pig intestine. Retrieved from http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3224308/
YouTube. Pharmacology. Pharmacology Lab Procedures. Setting Up the Organ Bath. Retrieved from https://www.youtube.com/watch?v=8_c7SojZKK4
WebMD. Digestive Disorders Health Centre. Histamine H2 Acid Reducers for Peptic Ulcer Disease. Retrieved from http://www.webmd.com/digestive-disorders/histamine-h2-acid-reducers-for-peptic-ulcer-disease
NCBI. Resources. Atropine Sulphate enhances neuromuscular transmission in a rat. Retrieved from http://www.ncbi.nlm.nih.gov/pubmed/2825461