Figure 10.

Blocking ON bipolar cells or glycine receptors suppresses the effect of TPMPA on the frequency response of OFF ganglion cells. A₁, Power spectra of excitatory currents from an OFF ganglion cell (G5) normalized by the peak power. TPMPA shifted power to low frequencies. A₂, Adding l-AP4 beforehand to block the ON bipolar cell reduced the effect of TPMPA on frequency response. A₃, A plot of change in middle frequency attributable to TPMPA with l-AP4 added beforehand against the change attributable to TPMPA alone (4 G5 cells). Cells lie near 100% when l-AP4 is added beforehand, but between 70 and 90% without l-AP4, indicating that l-AP4 prevents TPMPA from reducing middle frequency. B₁, Power spectra of excitatory currents from another OFF ganglion cell (G5) show that TPMPA shifted power to low frequencies. B₂, Adding strychnine beforehand to block glycine receptors reduced the effect of TPMPA on frequency response. B₃, A plot of change in middle frequency attributable to TPMPA with strychnine added beforehand against the change attributable to TPMPA alone (6 G5 cells, 1 unclassified). Cells lie near 100% when strychnine is added beforehand, but between 70 and 90% without strychnine, indicating that strychnine prevents TPMPA from reducing middle frequency.