Functioning of catfish electroreceptors: relation between skin potential and receptor activity.

Properties of catfish electroceptors were investigated by simultaneous recording of the skin potential and the activity of an afferent nerve. 1. The normal threshold stimulus intensity induces a potential amplitude of about 10 to 30 muV across the skin (Table I). 2. The average spike frequency in the nerve increases approximately with the logarithm of the stimulus intensity (Fig. 1). 3. The direct current restoring the receptor activity in calcium deficient media makes the skin potential more negative. 4. Presumably, not the skin potential itself but a difference between the skin potential and the e.m.f. generated by the receptor epithelium influences receptor functioning. 5. Amplitude and phase characteristics can be described by a filter circuit (Fig. 4 and 5).