Fig. 1
From: The role of NMDA receptors in rat propofol self-administration
The X-axis represents the number of days of propofol self-administration training. The Y-axis represents the number of responses, with ● representing active nose-pokes and ○ representing inactive nose-poke. As the number of training days increases, the numbers of active nose-pokes rose significantly relative to the number of inactive nose-pokes in study animals (P < 0.01), rats exhibited stable responses after a total of 14 training sessions