Fig. 4.

Receptor responses to GABA and acetylcholine injections in the lamina. A, Axonal recordings of receptor responses to 1.0 sec pulses of 1.0 mm GABA (pipette concentration) at varied injection pressures are shown. Injection volume was linear with pressure, and 20 psi produced a 100 nl volume. Each trace is the average of five responses.B, ACh was injected in 100 nl volumes from a multibarrel pipette with pipette concentrations of 1.0, 10, 100, and 1000 μm (as indicated above each trace). Eachtrace is the average of four responses.