Fig. 4. Effects of 8-bromoguanosine 3',5'-cyclic monophosphate (8-Br-cGMP) on the swim motor program. The control recording showing typical fictive swimming. Six minutes after the addition of 1 mmol l^–1 8-Br-cGMP, the pattern changed to one with a longer swim cycle and less consistency in the pattern. These effects were totally reversible after only a 2-min wash in seawater. This pattern was similar to the results with the NO donors and is thus suggestive of the involvement of a cGMP-dependent pathway in modulation of the swim central pattern generator by NO. All recordings were from the same cell.