striatum neuron GABA-Chol neuron GABAergic interneuron striatal cholinergic-GABAergic neuron STR Cholinergic GABA CGIN Although they constitute only 1–3% of all striatal neurons, these interneurons form a major modulatory hub, integrating cortical, thalamic, and dopaminergic inputs and shaping striatal output dynamics (Gonzales & Smith, 2015; Wegman et al., 2024). Electrophysiologically, the neuron exhibits tonic autonomous firing at 3–10 Hz, broad action potentials, and a prominent hyperpolarization-activated inward current (Ih) (Bennett & Wilson, 1999; Goldberg & Reynolds, 2011). Functionally, it modulates corticostriatal and thalamostriatal synaptic transmission, dopamine release, and spiny projection neuron excitability through co-transmission of acetylcholine and GABA (Lozovaya et al., 2018; Wegman et al., 2024). This dual inhibitory and modulatory signaling underlies context-dependent control of synaptic plasticity, action selection, and reinforcement learning (Gonzales & Smith, 2015; Lozovaya et al., 2018). A large aspiny interneuron of the striatum that serves as the principal intrinsic source of acetylcholine while simultaneously releasing GABA. It is defined by coexpression of cholinergic markers (ChAT and VAChT/Slc18a3) and GABAergic markers (GAD65/Gad2 and VGAT/Slc32a1) (Lozovaya et al., 2018). This MGE-derived neuron maintains Lhx6 expression associated with dual-transmitter identity (Fragkouli et al., 2009; Marin et al., 2000). Morphologically, it possesses a large soma (20–50 μm diameter), 2–4 thick aspiny dendrites extending radially ~1 mm, and locally ramified axons with hundreds of thousands of varicosities (Wilson et al., 1990; Lim et al., 2014).