Acetylcholine Lab Report

Introduction

The purpose of the experiment was to see the effect Acetylcholine (an agonist) had on the rate of contraction of isolated guinea pig ileum. Acetylcholine is a main neurotransmitter in both the peripheral and central nervous systems. An agonist is a chemical that binds to a receptor and activates the receptor to produce a biological response thereby enhancing the normal response. Acetylcholine is secreted by the post ganglionic neutron in the parasympathetic system this mediates contraction in smooth muscle via the type 2 muscarinic receptors (Flavio 2018). Muscarinic receptors are G-protein linked (Gq) which up regulate phospholipase C and thereby inositol triphosphate giving a rise to intracellular calcium. Activation of M3

The first time attaching the ileum the the organ bath it ripped, therefore we cut off the ripped section and retied it, this time in the organ bath with no issues. Key parts of the protocol include preparing the Tyrode’s solution required to keep ileum alive in the bath, proper tying of the piece of ileum (tied off on both sides, loop on side in solution so that contraction could increase without the ileum ripping, lumen is empty) so that it can be attached to the organ bath. The dose cycle is as follows 30 seconds to acquire baseline, add drug at 30s, 90s washout, 120s washout tissue again, then allow tissue to rest for 4 mins before adding drug. Washout is essential because it will remove any Ach left in Tyrode’s and removing it from the tissue so it doesn’t affect the concentrations of Ach being tested to follow. It was necessary that the ileum piece when relaxed showed zero peristalsis (Bernheim, 1934). Using the lowest concentration of Ach first then increasing it to allow for more precise readings. The controls of the experiment include same ileum used throughout the experiment, in the same organ bath always in Tyrode’s solution connected to the same