Fig. 3. Effects of S-nitroso-N-acetylpenicillamine (SNAP) on the swim motor program. (A) Control recording showing typical fictive swimming. Seven minutes after the addition of 1 mmol l^–1 SNAP, the period of the swim rhythm increased and became more erratic. This effect was not completely reversible, as indicated by a gradual return to a shorter swim cycle and a more consistent bursting pattern after a 20 min wash in seawater. (B) Reduced oxyhemoglobin blocked the effects of 1 mmol l^–1 SNAP. All recordings were from the same cell.