The Cholinergic Interneuron of the Striatum

Cholinergic interneurons make up a tiny fraction of cells in the striatum, but yet are critical modulators of neuronal excitability, synaptic transmission, and synaptic plasticity within the striatal circuitry, primarily through activation of muscarinic receptors. Cholinergic interneurons are tonically active in primates and rodents, and display various rhythmic and irregular firing patterns that are generated autonomously. A pause in their ongoing activity represents the motivational value of external stimuli. Cholinergic interneurons receive extrinsic input from various brain regions, notably glutamatergic input from cortex and thalamus, dopaminergic input from the substantia nigra pars compacta, and GABAergic input primarily of striatal origin. Here, we briefly review what is known about the biophysics of these neurons and of their neuromodulatory role. In addition, we review recent findings that underscore the fast nicotinic action of cholinergic interneurons on striatal circuitry, especially when these neurons are activated synchronously.