Subjects displayed increased sensitivity over time to constant 49°C, 40 s stimuli (A, Peak VAS) and to 49-50-49°C stimuli (B, MaxT2). However, minimum values during offset analgesia were not significantly altered following naloxone or remifentanil administration (C, Min Offset). Likewise, Magnitude Offset Analgesia (MaxT2 – Min Offset) was also not significantly altered (D). Time to the minimum ratings of offset analgesia was shorter following remifentanil compared to naloxone (E, Min Offset Latency), however, no after sensations were observed (F, VAS End Latency). Mean ± SEM; VAS, visual analogue scale.