Table of ContentsIntroductionMethodData ManagementDiscussionIntroductionThe ileum is the longest segment of the small intestine and contains a circular smooth muscle layer. Smooth muscle contains muscarinic acetylcholine receptors that are expected to respond to the presence of acetylcholine (ACh) and initiate muscle contraction (Widmaier et al., 2016). The purpose of this practical exercise was to examine the effect of increasing ACh concentrations on a segment of the guinea pig ileum. This was done by calculating the EC50 which is the concertation of the agonist which produces 50% of the maximum response and the Emax which is the maximum response produced by the agonist (Rang et al., 2016). It is expected that there will be a positive correlation between the concentration of ACh and the force of tissue contractions. Say no to plagiarism. Get a tailor-made essay on “Why Violent Video Games Should Not Be Banned”? Get the original essay MethodA guinea pig was humanely killed by cervical dislocation and the ileum was removed. A short segment of ileum (1 cm to 1.5 cm) was threaded at each end and mounted in a 38 ml organ bath. The organ bath containing aerated Tyrode's solution was maintained at a temperature of 36°C. The ileum segment was attached to one end of a lever connected to an isotonic transducer so that the tension of contractions could be recorded in the Powerlab data collection device. A 1 g weight was attached to the other end of the lever so that the fabric was under tension. Addition of AcetylcholineA range of serial dilutions of acetylcholine (ACh) was carried out to produce final organ bath concentrations between 1*10-9M and 8.192*10-6 M. ACh was added in a 3 minute dose cycle. The lowest concentration of ACh was added to the organ bath and the tissue response was observed for 30 seconds. The solution was washed by overflow to remove ACh. In order for the temperature to equilibrate, the fabric was left to rest for two minutes. Increasing concentrations of ACh were added to the organ bath in double increments and the tissue response was recorded until a maximal response was reached. Data processing A data trace was produced in LabChart. This was used to calculate the value of Emax and to calculate the percentage of maximum response from the recorded voltages. A plot of percent maximum response versus log[ACh(M)] was produced in Microsoft Excel. From the graph, the EC50 value was calculated. Figure 1: Graph showing the response of a short segment of guinea pig ileum to increasing concentrations of acetylcholine. Data is expressed as a percentage of the maximum response recorded in millivolts. The graph shows an EC50 value of 3.98*10-8 M (dashed line). Figure 2: Data trace showing the effects of different concentrations of ACh on a guinea pig ileum segment. Data are expressed as tissue contraction force in millivolts. As shown in Figure 1, there is a positive correlation between the concentration of ACh and the strength of the recorded contractions. ACh produced little contraction in tissues until a threshold concentration of 4*10-6M was reached. From 4*10-9M to 1.6*10-8M, there was little difference in the strength of contractions. However, there was a sharp increase in the force of tissue contractions between 1.6*10-8M and 6.4*10-8M. Maximum response was recorded at an ACh concentration of 2.56*10-7M. At higher concentrations of ACh, Figure 1 shows a decrease in the force of contractions. ACh produced a pEC50 value of 7.4 and Figure 2 shows that it produced a.