Fig. 2. The effects of nitric oxide synthase (NOS) inhibitors on (A) noradrenaline (unfilled bars), adrenaline (filled bars) and total catecholamine (sum of noradrenaline + adrenaline) and (B) nitric oxide (NO) secretion rates over a 10 min period in response to a bolus injection of 10 mmol l^–1 KCl in a perfused posterior cardinal vein preparation of rainbow trout. Preparations were either pre-treated with saline (N=6) or with saline containing the combination of the NOS inhibitors 7-NI (10^–4 mol l^–1) and L-NAME (5x10^–3 mol l^–1; cross-hatched bars; N=6). Values are means ± 1 S.E.M. A dagger denotes a significant difference (P<0.5) between pre-KCl and post-KCl samples. An asterisk denotes a significant difference (P<0.5) between the control and the inhibitor treated group (cross-hatched).