Figure 6.

Pretreatment (24 hr) with 20 mg·kg⁻¹ i.p. propranolol inhibited dextrorphan (DOR) formation in vivo and in vitro in liver microsomes from TG and WT mice. After 24 hr i.p. pretreatment with either saline or propranolol, all mice were given an i.p. injection of 30 mg·kg⁻¹ of dextromethorphan (DEX) and blood was collected via saphenous vein 30 min after dextromethorphan injection. In (a) and (b), the in vivo serum dextrorphan/dextromethorphan ratio, serum dextrorphan and serum dextromethorphan levels in TG and WT mice were assessed. In (c) and (d), the dextrorphan formation by liver microsomes (0.1 mg·ml⁻¹) prepared from pretreated mice was assessed after incubation with dextromethorphan (5 µM) for 10 min. Data presented are expressed as mean (with SEM) values of individual animals normalized to the saline pretreated group, within the same mouse line. *P < .05, significantly different from saline pretreated group; two‐tailed, unpaired t test on the raw data