The effects of ciguatoxin on the nerves of the teleost fish, Sillago ciliata.

The absolute refractory period, relative refractory period, and the duration and magnitude of the supernormal period were measured after incubation of fish nerves with ciguatoxin and other channel modifying compounds, tetrodotoxin, veratridine, verapamil, and lignocaine. In vitro electrophysiological studies were carried out on the lateral line nerve of the whiting, Sillago ciliata Cuvier. Electrophysiological changes in fish nerves after exposure to ciguatoxin (0.3 MU.ml-1) and veratridine (1 x 10(-5) M) are similar to changes that occur in mammalian nerves and include an increase in the absolute refractory period, the relative refractory period, and the magnitude and duration of supernormality. The effects of ciguatoxin (0.3 MU.ml-1) in fish nerves were antagonised by tetrodotoxin (5 x 10(-10) M), verapamil (5 x 10(-7) M), and lignocaine (1 x 10(-5) g/ml-1). The nerves of Sillago ciliata used in this study responded to ciguatoxin and its antagonists in a similar manner to mammalian nerves, suggesting that these teleost nerves have no specific electrophysiological mechanism to cope with this toxin.