Fig. 3.
The effects of morphine on lactic acid–induced impairment of visual attention performance. (A) Morphine reduced the effect of 1.8% lactic acid on performance as measured with median cue duration in a dose-dependent manner (F[4,47] = 19.4, P < 0.0001). Saline and morphine at any dose had no effect on median cue duration in the absence of lactic acid administration. *P < 0.05 compared with baseline; #P < 0.05 compared with saline/saline; $P < 0.05 compared with saline/1.8% lactic acid; &P > 0.05 compared with 0.3 morphine/1.8% lactic acid. Mean and SD are shown, N = 8 to 14/group. (B) Representative visual cue duration titration curves are shown following treatment with 1.8% lactic acid in combination with indicated doses of morphine or no treatment (baseline). Each curve represents an individual session of 100 trials on a given day and treatment.