Phys 173 / BGGN 266 LPA Induced Cl-Oscillations in Xenopus Oocytes

If only we hadn't poked these oocytes, how cute would it be! INTRODUCTION Electrophysiology in the Xenopus oocyte began in 1982 when scientists realized that they could inject mRNA into oocytes and express functional ion channels and receptors. Since this time scientists have utilized this important technique to study several aspects of the structure and function of ion channels and receptors. These include: (1) Analyzing the properties of mutated channels as a means to understand the structure-function relationships in ion channels. (2) Studying the post-translational processing and the assembly of multisubunit channels and receptors. (3) Comparing the properties of channels from various tissues expressed in a common environment. (4) Examining the modulation of channel and receptor function by various second messenger systems. (5) Analyzing various aspects of receptor-effector coupling. (6) Functional screening of cloned genes that encode channels and receptors. Most of these experiments require electrophysiological recording from oocytes. It is therefore important to have a basic understanding of the oocytes and the techniques used to record from them. Xenopus oocytes are the precursor to frog eggs, the difference being that they have not undergone the proper hormonal stimulation to mature. The oocyte is a large cell, with a diameter of ~1-1.2mm making them ideal for electrophysiological recordings. The spherical structure (fig 1.) of the oocyte is characterized by two distinct hemispheres; the animal pole (dark) and the vegetal pole (light), the animal pole being where the nucleus is located. Another important structural component of the oocyte is the follicle cell layer. The follicle cell layer is a source of many potential problems, the first being one of practicality. It is harder to poke an oocyte when it has its follicle cell layer attached. Another potential problem is that there is electrical coupling between cells in the follicle cell layer, which can be mistaken as electrical events occurring inside the oocyte. For these reasons, it is important to remove the follicle cell layer before poking the oocyte (see lab manual). AMENDED PROCEDURE We closely followed the procedure describe in the 2001 Lab Manual for Oocyte Biophysics making only a few modifications. Our goal was to introduce goat serum containing LPA into the oocytes bath and observe Cl-oscillations. A detailed explanation of the cascade that produces these oscillations is to follow in the next section. One departure from the given procedure was the concentration of goat serum that we exposed the …