Figure 6.

Time course of nociceptive responses to mechanical and heat stimuli after a single systemic treatment with morphine. Animals were injected with morphine (3 mg/kg, subcutaneous) and responses to mechanical and heat stimuli measured. Morphine treatment of alcohol and high fat (AHF) fed rats decreased the number of responses to (A) low (1 g) and (B) high intensity (6 g) mechanical stimulation of the abdominal skin for up to 4 h. Abdominal withdrawal responses of controls evoked by high intensity (6 g) mechanical stimulation were reduced 1 h after treatment compared to before morphine. Hindpaw (C) mechanical withdrawal thresholds and (D) response latencies on the hot plate test of AHF fed rats were improved at 1 and 4 h after morphine treatment. Controls were unaffected by the low dose morphine. ^aP < 0.05, AHF vs control.