Figure 1: Starburst amacrine cell-mediated cholinergic excitation and GABAergic inhibition.
(a) Reconstruction of a connected pair of ON-SAC (green) and ON-DSGCs (black). (b) Paired recording revealed the obligatory co-release of ACh and GABA from ON-SACs. Overlain voltage traces show the transformation of SAC-driven synaptic excitation of an ON-DSGC to synaptic inhibition when nAChRs were blocked with Mecamylamine (MMA, 10 μM, blue traces; action potentials (APs) have been truncated for clarity). The lower traces show the somatic current-evoked excitation of the ON-SAC. (c) Cumulative probability distributions of the amplitude of each SAC-evoked PSP recorded under the indicated conditions, from the indicated number of paired recordings. (d) In a different pair of ON-SAC and ON-DSGCs net inhibition was generated under control conditions, which was transformed to excitation by the blockade of GABAA receptors (SR-95531 (GABAzine), 10 μM, red; morphologies shown in a). (e) Cumulative probability distributions of PSP amplitude under the indicated conditions. (f) Onset latency of pharmacologically isolated excitatory and inhibitory PSPs, recorded in GABAzine (n=7) and MMA (n=7), respectively. Onset latency was measured from the onset of the presynaptic driving current to 5% of the peak of the postsynaptic response. (g) Averaged pharmacologically isolated excitatory and inhibitory PSPs, the vertical dashed line indicates the onset time of the presynaptic driving current. (h) Upper overlain traces show the biphasic waveform (sum, black trace) produced by the arithmetic summation of isolated excitatory and inhibitory PSPs. The lower trace shows an averaged PSP recorded under control conditions, note the biphasic waveform.
