Reduction of serotonin-induced hypersensitivity by SAM and β
antagonism. In all graphs, symbols represent mean ± SEM withdrawal threshold (g). In both experiments, serotonin (5-HT) was injected into one hind paw and withdrawal thresholds were assessed over a 4–h period. ( A) Pretreatment with 80 mg/kg SAM (5-HT + SAM) lowers 5-HT-induced hypersensitivity compared to saline-pretreated mice (5-HT + Saline). SAM alone (Saline + SAM) produced no changes in withdrawal threshold at any time point. ( B) Administration of the selective β2 and β3 antagonists, ICI118,551 and SR59230A (5-HT + ICI/SR), reduces 5-HT-induced hypersensitivity compared to saline controls (5-HT + Saline). ICI/SR alone (Saline + ICI/SR) produced no changes in withdrawal threshold at any time point.