Fig. 1. The effects of acute hypoxia (40 mmHg=5.3 kPa; at the vertical dashed line) on plasma levels of adrenaline (filled columns) and noradrenaline (open columns) in rainbow trout (Oncorhynchus mykiss) previously infused (0.2 ml min^–1) with (A) saline (N=9) or (B) nicotine (1.3x10^–5 mol kg^–1 h^–1; N=17) for 60 min under conditions of normoxia. Plasma catecholamine levels were measured at ‘Pre’, 10 min and 60 min of infusion and during acute hypoxia. Values are shown as means + S.E.M. An asterisk denotes a statistically significant increase (P<0.05) from the corresponding ‘Pre’ value or ‘60 min’ pre-hypoxia value. A dagger indicates a statistically significant difference (P<0.05) from the control (saline-infused) value.