Inhibition of Spontaneous Lateral-line Activity by Efferent Nerve Stimulation

In common with other acoustico-lateralis receptors, the hair cells of the lateral-line organs of fishes and amphibia receive efferent innervation. Ultrastructural studies have shown that efferent synapses similar to those found at the base of the hair cells in the cochlea (Engstrom & Wersall, 1958) and vestibular system (Wersall, 1956) exist also at the base of hair cells in lateral-line organs (Hama, 1965; Flock, 1965, 1967), including those of sharks and dogfish (Hama, 1970; Roberts & Ryan, 1971). Furthermore, efferent impulses have been recorded from lateral-line nerves in amphibia (Schmidt, 1965; Gorner, 1967; Russell, 1971), in teleost fish (Hashimoto, Katsuki & Yanagisawa, 1970) and in elasmobranchs (Roberts & Russell, 1970). In cases where the function of the efferent system has been studied, namely in the cochlea (Galambos, 1956; Fex, 1962), in the vestibular systems of fishes (Klinke & Schmidt, 1970), of amphibia (Gleissner & Henriksson, 1964; Llinas & Precht, 1969; Goetmakers & Groen, 1970) and of mammals (Sala, 1965) and in the lateralline systems of the eel, Astroconger myriaster (Hashimoto et al. 1970) and of Xenopus laevis (Russell, 1968, 1971), it has been shown that stimulation of the efferent fibres can lead to inhibition of impulse activity in the primary afferent fibres. The experiments described in this paper were designed to show whether efferent fibres could be made to exert an inhibitory effect on the lateral-line sense organs of dogfish.