20% CO2-induced panic provocation model and cardiovascular response in rats

Experiments were performed in male Sprague–Dawley rats (300–350 g, Harlan Laboratory, Indianapolis, IN) as previously described, using a counterbalanced design¹². JNJ-63821238, the less active enantiomer of JNJ-61393215, was included as a negative control, and was formulated in the same vehicle. The social interaction test, a fully validated test of experimental anxiety-like behavior in rats, was performed in the open-field arena^22,23. Both the “experimental” rat and an unfamiliar “partner” rat are placed in the center of the box, and the total duration (seconds) of nonaggressive physical contact (grooming, sniffing, crawling over and under, etc.) initiated by the “experimental” rat is quantified over 5 min. All behaviors were videotaped, and sessions were scored using ANY-maze (Stoelting, Wood Dale, IL) for open field (Stoelting), or by Stephanie D. Fitz (blind to treatments) for social interaction. Each dependent variable for assessment of behavior and radiotelemetry data was respectively analyzed using a one-way ANOVA, or a one-way ANOVA with repeated measures with drug treatment as the main factor and time as repeated measure. In the presence of significant main effects, post hoc tests were conducted using a parametric Fisher’s LSD test. Within-subject’s time effects were also assessed using Dunnett’s one-way analysis with the minute prior to the i.v. infusion used as the control. Statistical significance was accepted with P < 0.05. All statistical analyses were carried out using SPSS 13.0 (SPSS Inc., IL, USA), and all graphs were generated using SigmaPlot 2001 (SPSS Inc., IL, USA) or Graphpad Prizm 7 Software Inc. for Windows. No randomization was used.