Fig. 7.

Photoreceptor responses recorded in the axon to pressure injections of TRP in the lamina. Stimulus duration (bottomtrace) was 100 msec, and the pressure was varied to produce different injection volumes of a 10 μm TRP solution in the pipette (topfourtraces). The numbersabove each trace indicate the gram-equivalent injection dose in picomolar concentrations. Each trace is the average of three to five responses. Note that at 0.87 pm, the response appears to occur in two phases. The second phase (i.e., the large delayed hyperpolarization) was commonly observed with large injection volumes (0.1 μl).