Fig. 6. The effects of in situ electrical stimulation on (A) total catecholamine secretion (sum of noradrenaline plus adrenaline) and (B) perfusate NO_X levels in preparations derived from fish repeatedly exposed to hypoxia (unfilled bars; N=9) or from control fish (filled bars; N=9). Following the stabilization period, the preparations were perfused with control saline or saline containing a cocktail of NOS inhibitors (cross-hatched bars) and electrically stimulated at 30 V and 8 Hz. Values are shown as means ± 1 s.e.m. A dagger denotes a significant difference (P<0.5) between pre-experimental (Pre) and stimulated samples. An asterisk denotes a significant difference (P<0.5) between the hypoxia-treated preparations with or without NOS inhibitors.