An antistrychnine extract from horse intestine

Gaddum, J. H.; Randić, Mirjana; Smith, M. W.

doi:10.1113/jphysiol.1964.sp007413

Cited by 13 publications

(1 citation statement)

References 6 publications

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“…The factors controlling the steepness of the curve are largely unknown. In the assays described by Gaddum, Randi6 & Smith (1964) a rat uterus and a pendulum lever were used to assay extracts of horse intestine. The log dose/effect was flat and the result depended on (2 + 2) dose assays, in which the ratio of large to small doses was 2.…”

Section: An Improved Microba Thmentioning

confidence: 99%

An Improved Microbath

Gaddum

1964

British Journal of Pharmacology and Chemotherapy

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A method is described for the study of the actions of drugs and tissue extracts on small pieces of smooth muscle suspended in a bath with a capacity of 0.027 ml. The small size of the bath is an advantage when the total amount of active substance is small. The contractions are amplified 50-to 500-times and recorded isotonically, or approximately isometrically, with a pen writer. This apparatus has the advantage over earlier models that it is more compact and convenient and that the temperature of the muscle can be controlled. It has been used for the estimation of small quantities of acetylcholine and other substances in tissue extracts.Most of our knowledge of the physiological importance of acetylcholine and other pharmacologically active substances, which are found in extracts of tissues, is based on bioassays and many of these bioassays depend on the contractions of various isolated muscles. At one time the volume of the bath in which these muscles were suspended was about 100 ml., but this volume has gradually been reduced in order to increase the sensitivity of the test. In the technique known as superfusion (Gaddum, 1953;Adam, Hardwick & Spencer, 1954) the muscle is suspended in air and the solution runs over its surface. The solutions to be tested are then applied, in suitable dilutions, directly to the muscle, while the flow of the solution may be temporarily stopped to give the active substances time to act. When this technique is used, the volume of fluid in which the drug is dissolved is generally about 0.5 ml. A smaller volume will not replace the fluid on the surface of the strips of muscle normally used, and superfusion of smaller pieces of muscle is complicated by effects due to surface tension. These considerations led Gaddum & Stephenson (1958) and Gaddum & Szerb (1961) to construct a microbath with a volume of about 0.025 ml. The muscle was attached to an isotonic lever carrying a mirror which reflected a light on to a photocell, from which an amplified current controlled a pen writer. This apparatus gave satisfactory results at room temperature, but was not satisfactory at higher temperatures, and a series of more complicated baths were made before the simple one described here was devised. The object of the present paper is to describe this bath, which can be used at any temperature. The original lever and amplifying current have been replaced by a compact apparatus with transistors. METHODSThe microbath. In earlier models the bath was horizontal. In the present model it is vertical (Fig. 1, 1) and is made from a block of Perspex (65 x 30 x 12 mm). It is attached to a brass rod, which is held in a Palmer rack-and-pinion block (2), which gives coarse and

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Section: An Improved Microba Thmentioning

confidence: 99%