Acetylcholine Receptors Lab Report

Receptors

Receptors specifically bind to target molecules and initiate a response in the target cell. In most cases, these receptors are transmembrane proteins on the cell surface. When an extracellular signal molecule binds to them, they release a cascade of intracellular signals that alter the behavior of the cell1. In this experiment, we will be adding compounds, such as eserine and acetylcholine to a muscle cell bath and measuring its effect, in this case being force of contraction. These compounds target muscarinic acetylcholine receptors to produce their response, which will be made into a concentration/effect curve.

Muscarinic acetylcholine receptors

The muscarinic acetylcholine receptor (MAR) is a G protein– coupled receptor whose activation leads to opening of K+channels and subsequent hyperpolarization of the plasma membrane2. The binding of acetylcholine leads to the activation of a G protein, which binds to and releases ion channels. These ion channels can allow a varity of ions to move in or out of the cell, including K+, Na+ and Ca2+. There are five different types of MAR, M1-M5. Contraction of the bladder involves direct contraction of the M3 and an indirect re-contraction by the M2-receptors3. These are the receptors that we will be

The effect is produced as the ligand binds to the receptor. Therefore, the more ligand you have, the more receptors you are able to stimulate/inhibit. As concentration of the drug increases, its effect will also increase5. However, once all carrier sites become occupied, further increases in drug concentration will not produce further increments in drug influx5. In this experiment, we will be determining the effect of increasing concentration of drugs like eserine and acetylcholine on muscle tissue response, at what concentration levels effect increases fastest, as well as where a further increase will yield no further