Fig. 4. The effect of inhibiting NO synthesis by bath application of the NOS inhibitor L-NAME. (Ai) A 10 min bath application of 20 mmol l^–1 L-NAME caused a statistically significant decrease in the cycle frequency of the digging rhythm (t=2.08, ^*P<0.05, mean ± s.e.m. from eight animals). (Aii) The effects of L-NAME were reversed by a 30 min wash with locust saline. (Bi) A 10 min bath application of the inactive isomer 20 mmol l^–1 D-NAME caused no statistically significant change in cycle frequency (t=0.12, P>0.05, mean ± s.e.m. from four animals). (Bii) An example showing that a 10 min bath application of 20 mmol l^–1 D-NAME resulted in no significant decrease in the number of cycles between test and control values.