Fig. 2.

Behavioral analyses of EP1-deficient mice (A) Electric-shock-induced fighting behavior. Age-matched pairs of male wild-type or Ptger1^-/- mice (n = 8 pairs for each) were placed in a transparent container and exposed to electric shock for 3 min. The latency to the first fighting episode, the number of fighting events, and the total duration of fighting were counted. **, P < 0.001 vs. wild type. (B) Open-field test. Individual wild-type (n = 12) or Ptger1^-/- (n = 11) mice were allowed to explore freely the open field for 5 min. Ambulation was measured with an automatic infrared beam counter, and the occurrence of each typical behavior (rearing, grooming, urination, defecation, jumping) was scored from a video recording. **, P < 0.01 vs. wild type. (C) Acoustic startle reflex. Wild-type or Ptger1^-/- mice (n = 16 for each) were placed in a startle chamber, and the startle reflex to audible stimuli of the indicated frequencies was measured. Background noise (BG) is 70 dB. **, P < 0.01 vs. corresponding value for wild type. (D) Impaired cliff avoidance in Ptger1^-/- mice. Wild-type or Ptger1^-/- mice were placed on the base of an inverted glass beaker, and their behavior was recorded with a video camera (see Movie 3). (E) The cumulative frequency of jumping for Ptger1^-/- (red circles), Ptger3^-/- (blue inverted triangles), or wild-type (black triangles) mice (n = 7 for each) and for wild-type mice injected with ONO-8713 (10 mg/kg i.p.) 1 h before the test (green triangles, n = 6) was determined over 7 min in the cliff-avoidance test. **, P < 0.01, ***, P < 0.001 vs. nontreated wild-type mice.