Fig. 5.

Effects of saline, serotonin, and male–male social interaction on the EOD waveform. (A) Effects on EOD amplitude and repolarization time (τ-P2). Changes due to circadian rhythm have been removed as described in Materials and methods (Fig. 3). (B) EOD waveforms sampled immediately before injection and at the time of peak effect. In the case of the saline injection (male 122) the two waveforms superimpose almost completely. Effects of serotonin varied between individuals. In some males (e.g. male 042), amplitude and τ-P2 both increased, whereas in others (e.g. male 036), repolarization time increased alone. Both males received saturating doses of 5-HT as indicated in Fig. 7 (male 042: 2.5 nmol g⁻¹; male 036: 25 nmol g⁻¹). Note the difference in the time courses of the τ-P2 response as well (see Fig. 8). As part of a different experiment, male 222 had a second male placed briefly in his hiding tube (first broken line). EOD amplitude and τ-P2 increased in a manner similar to EODs of fish injected with serotonin, then declined following the second male’s removal (second broken line).