Fig. 9. (A,B) Average intensity—response curves showing that quipazine (10 pmol) suppressed medulla bilateral neuron (MBN) photo-responsiveness during both day and night, but more effectively during the night. Filled and open circles indicate results before and after quipazine injection, respectively. Vertical bars indicate ± 1 S.E.M. (B) Dose dependency of the effect of quipazine on MBN photo-responsiveness. Open and filled squares indicate results for the day and night, respectively. Values are means ± S.E.M. of 4-8 preparations. a and b indicate a significant difference (P<0.01, t-test) compared with Ringer-injected control value for day and night, respectively. c indicates a significant difference between day and night values (P<0.01, t-test).