In the present manuscript, escalation sessions were identified as such when one of the two groups of animals escalated as assessed by a one-tailed paired sample t-test comparing their performance on the most recent test session to the session immediately prior to the most recent session. To evaluate the effects of acute and chronic MMP inhibition on the development escalated ethanol self-administration, a mixed model two-way ANOVA was utilized with drug treatment and post-vapor session as the between-and within-subjects factors, respectively. In the acute and chronic FN-439 experiments, for the within-subject variable of session, the initial post-vapor exposure session(s) were compared to the session in which escalation of responding occurred. In the chronic FN-439 exposure experiment, only one initial test session took place prior to escalation. However, in the acute FN-439 treatment experiment, three sessions took place prior to escalation and in order to maintain consistent data analysis across experiments, the averages of those three sessions were used as the initial test session values in the two-way ANOVA. The acceptability of this action was determined by conducting one-way repeated-measures ANOVAs
