An entry for the Gunning Memorial (Victoria Jubilee) Fund Prize in Physiology (Bell Prize), 1988

The aim of these experiments has been to find a means of identifying the primary afferent axons from b2c spindle units (b2c afferents) of tandem muscle spindles in the cat. The drug succinylcholine has been used to activate the intrafusal bag fibres of muscle spindles in various muscles. In all the muscles studied, several patterns of afferent response to SCh have been seen, of which one is exactly that predicted for b2c afferents on the basis of the known properties of the bag fibres. Additional support for this identification comes from the fact that these afferents are often diagnosed as primaries on the basis of other tests including the axonal conduction velocity, the coefficient of variation of the resting discharge, the sensitivity to sinusoidal muscle stretch and the sensitivity to small -amplitude, high frequency vibration of the parent muscle, and all this in a number of different muscles: Preliminary histological evidence further supports this conclusion; only one b2c afferent has been found in tenuissimus to date, but the region of the muscle in which it terminated was shown to contain a b2c spindle unit. It is concluded that SCh activation is a simple and reliable means of identifying b2c afferents and that this test can be used to classify afferents which many, if not all, of the other commonly used tests would leave unclassifed. The aim of these experiments has been to find a means of identifying the primary afferent axons from b2c spindle units (b2c afferents) of tandem muscle spindles in the cat. The drug succinylcholine has been used to activate the intrafusal bag fibres of muscle spindles in various muscles. In all the muscles studied, several patterns of afferent response to SCh have been seen, of which one is exactly that predicted for b2c afferents on the basis of the known properties of the bag fibres. Additional support for this identification comes from the fact that these afferents are often diagnosed as primaries on the basis of other tests including the axonal conduction velocity, the coefficient of variation of the resting discharge, the sensitivity to sinusoidal muscle stretch and the sensitivity to small -amplitude, high frequency vibration of the parent muscle, and all this in a number of different muscles: Preliminary histological evidence further supports this conclusion; only one b2c afferent has been found in tenuissimus to date, but the region of the muscle in which it terminated was shown to contain a b2c spindle unit. It is concluded that SCh activation is a simple and reliable means of identifying b2c afferents and that this test can be used to classify afferents which many, if not all, of the other commonly used tests would leave unclassifed.