Fig. 2.

D1 and D2 SPNs possess distinct physiological properties. (A) Asymmetric connectivity between D1 and D2 SPNs. About 5% of D1 SPNs target D2 SPNs, whereas other synaptic connections vary within the 25–35% range. (B) Distinct GABAergic dynamics in D1 and D2 SPNs. Synapses emerging from D1 SPNs have higher GABAergic conductance [see the difference in amplitude of the first inhibitory postsynaptic current (IPSC)], but they are depressed more rapidly (see the evolution of IPSC amplitudes). (C) Higher activation of outward calcium-dependent potassium currents in D2 SPNs. Upper shows the protocol of injected current that is applied to D1 and D2 SPNs in the model. Lower shows earlier and stronger activation of the channel in D2 SPNs.