Fig. 2

Positive conditioning increases the number of cataplexy-like behaviors. For this study, we used three male (black dots and lines) and four female (red dots and lines) orexin neuron ablated mice. A The preference score was calculated by dividing the time spent in the treatment-paired chamber by the total time spent in both chambers. None of the animals had an initial bias (preference score > 0.8 or < 0.2) for either chamber. Two days of conditioning with chocolate successfully increased the preference score (2-way ANOVA). B-D The number of cataplexy-like behavior in the chocolate-associated chamber B, in the control chamber C, and total number D are shown. Bars indicate mean ± SEM of the mixed data from male and female mice. The number of cataplexy-like behaviors during pre- and post-conditioning periods was normalized by the stay time in the chamber. There was no need for such data normalization during conditioning-1 and conditioning-2 because the mice were confined to one chamber during the conditioning period. In the chocolate-associated chamber, cataplexy-like behavior significantly increased during the post-conditioning period compared to the pre-conditioning period. To examine whether there was a difference in the characteristics of cataplexy-like behavior among pre-conditioning, conditioning, and post-conditioning periods, we also calculated the duration of a single cataplexy-like episode. It did not change when the animal stayed in the chocolate-associated chamber E and the control chamber F. Together, positive conditioning seemed to affect the starting but not maintenance of cataplexy-like behavior. Statistical significances denoted in the figure were obtained by 2-way ANOVA in (A) and by repeated design one-way ANOVA followed by Sidak's multiple comparison test, if appropriate, in (B–F)