Proceedings of the Physiological Society, 21–22 March 1969, University College London Meeting: Demonstrations

Abstract

The apparatus demonstrated was designed to improve the precision of the methods used for the collection, manipulation and analysis of very small uncontaminated specimens of the inner ear fluids of the rat and for the measurement of the endolymphatic potentials in the same animals.To eliminate risk of deterioration in the animal's condition all the microdissection, electrical measurements and fluid collections were completed in both ears within 1 hr, making operative speed vital. These manipulations were greatly facilitated by the firm fixation of the head provided by a specially designed claw clamp, giving a firm four-point grip upon the edges of the bony plate connecting the superior margins of the orbits. The clamp was securely mounted in an arrangement of gimbals with their axes traversing the cochlea. With this positioned at the point of focus of the microscope it was easy to impart to it the critical orientations required.The recording and aspirating micropipettes were mounted upon a small micromanipulator carried upon an engineer's flexible snake-arm, by means of which the first coarse positioning of the pipette could be carried out with speed and accuracy. In order to make the clamp for the fixation of this snake-arm virtually dead-beat it was necessary to apply considerable tension to the central Bowden cable, leading to frequent avulsion of the terminal nipples. A novel method of construction was therefore devised which greatly increased the strength of these junctions.Satisfactory fluid specimens were subdivided into samples, generally 2 nl. in volume, for analysis and each sample diluted with 1 #1 of distilled water, enabling it to be stored in a silica pipette for periods of up to 7 days. To prevent contamination all these manipulations were carried out under C