Malapterurus electricus

The richest source of nicotinic acetylcholine receptors are the electric organs of the South American electric eel (Electrophorus electricus), the African electric catfish Malapterurus electricus) and the electric ray e.g. the marbled electric ray of the eastern Atlantic Ocean (Torpedo marmoratd) and the Californian electric ray in the northeastern Pacific (Torpedo califomica)) (Fig. 8.36). 

A radioactive perhydro-derivative of histrionicotoxin (pH]H,2-HTX (10, 92) has proved a very useful tool for investigation of the binding sites for histrionicotoxin in membranes and microsacs from Torpedo electroplax preparations (see Table 12 for references). Its use has not been extended to muscle preparations where the density of nicotinic receptor channel complexes are many fold lower than in Torpedo electroplax. Indeed, no specific binding could be detected in the electroplax of the Egyptian electric fish (Malapterurus electricus) where the density of nicotinic receptors also appear very low (97). In membranes from Torpedo electroplax pH]Hi2-HTX binds to a site with an affinity constant (Kd) of about 0.4 pM. The density of the binding sites for pH]Hi2 HTX is apparently about twice that of the acetylcholine-binding sites in electroplax membranes. The rate of... 

There are three species known with powerful electric organs and several others with weak electric organs. The most powerful species is the Electro-phoms electricus (Linnaeus), the so-called electric eel, which occurs in the Amazon in Brazil. The maximal discharge in medium sized specimens is on the average 400-600 volts, but may be in some individuals more than 800 volts. Another powerful species is the Malapterurus, which is found in... 

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