Figure 7. The reliability of dIN firing following 18-β-GA application.

A, 2 dINs show typical, reliable, 1 spike per cycle firing in swimming before 18-β-GA application. Swimming was started by electrical stimulation on the skin (*) and lasted for 93 s (grey bars show the break in recording). There is a typical swimming frequency drop from the beginning to the end of the episode. B, while the coupling block is progressing (44% of control), dIN1 only fires 1 spike while dIN2 still fires on the majority of swimming cycles. Swimming was spontaneous and just the start (dots indicate a brief sampling gap) and the end are shown (grey bars show the break in recording). C, when the 18-β-GA block is stable (12% of control), the swimming episode (started by skin stimulation at *) is shortened to ∼1.3 s. dIN1 fires 3 spikes while dIN2 still fires very reliably. D, summary of the changes in firing reliability of 16 dINs in 9 animals before block and in final 18-β-GA block. Lines indicate changes in individual neurons. E, time series plots of firing reliability (%) for 12 dINs in 6 paired recordings. Grey curves and symbols in the upper panel are 6 dINs which fired reliably throughout 18-β-GA application. Reliability for 6 dINs in the lower panel dropped gradually and then stayed at low levels. Filled symbols show averaged time series of firing reliability of all 12 dINs (mean ±s.d.). The time for the episodes illustrated in A, B and C is marked in E (open circles).