Fig. 2.

STD kinetics of neostriatal inhibitory synapses. From top to bottom, trains of IPSCs from each connection in response to a 20-Hz train of stimulus delivered at 0.1 Hz. (A) GP→NST. (B) SPN→SPN. (C) FS→SPN. (A–C) Black trace, average of 25 individual responses (gray). (D) STD kinetics: Normalized and averaged IPSC amplitudes evoked with stimulus trains. Lines are fits to: IPSC(t) = A₁e^−x/τ1 + A₂e^−x/τ2 + y0, where τ₁ is the faster time constant of decay (see Materials and Methods). Note virtually identical STD kinetics for SPN→SPN (unitary) and GP→NSt (population) connections and a slower decay for the FS→SPN connection. (E) Direct relationships between IPSC amplitudes and CV⁻² (r² > 0.9 for all connections; P < 0.002). Note the plot superimposition for SPN→SPN (unitary) and GP→NSt (population) connections and a separate relationship for the FS→SPN connection.