VINCRISTINE DISTURBS SPONTANEOUS FIRING OF THE AFFERENT NERVE-FIBER IN AMPULLARY ELECTRORECEPTOR ORGANS

Ampullary electroreceptor organs of the catfish were apically exposed to 0.3 mM vincristine in order to investigate the part played by the m icrotubular system in stimulus transduction. The main effects were rep etitive firing of the afferent fibre, a reduction of the mean spontane ous activity and a reduction of the spike amplitude two to four days a fter exposure to vincristine. The mean sensitivity was less susceptibl e to vincristine than the spontaneous activity. Since the shape of the frequency curves remained unchanged and similar effects as described above were also observed after denervation, we conclude that vincristi ne most likely does not affect electroreceptor cell functioning, but c auses degeneration of the afferent fibre.