Fig. 8. (A) Examples of electroretinogram (ERG) waveform recorded from the compound eye of the cricket before (a1) and after (a2) the optic nerve was severed. The response was elicited with a 500 ms light pulse (shown beneath ERG recordings). (B) ERG waveforms before (b1) and after (b2) 10nl of serotonin solution (10 mmoll^-1) was injected into the optic lobe. (C,D) Representative intensity—response curves for the on-component of the ERG obtained before (filled circles) and after (open circles) serotonin injection into the optic lobe during the day (C) and the night (D). Similar results were obtained in other preparations (day, N=3; night, N=3). Note that injection of serotonin into the optic lobe had no significant (P>0.05, N=4) effect on both waveform and amplitude of the ERG.