Cholinergic Interneurons Are Differentially Distributed in the Human Striatum (original) (raw)
Figure 6
Schematic drawings with functional considerations on the ChAT-ir interneurons.
A, difference in the density of cholinergic interneurons between the CN and Put. ChAT-ir neurons populate the matrix and the striosomes in the CN and Put but the number of these cells in the two compartments is higher in the former than in the latter. In both striatal components, the cholinergic interneurons abound at the boundaries between the two major compartments and the two striosomal regions. B, Variation in the activity of the cholinergic neurons defined as TANs depending on: 1, the presence or absence of a reward-associated stimulus and 2, their location in the matrix or within a striosome. _a–a_′, without stimulus the TANs constantly release ACh, which exerts a dual control on GABAergic interneurons through the nicotinic and muscarinic receptors. Due to the large amount of ACh release by these cholinergic neurons, the greater or lower amount of AChE might not be a limiting factor for the activation of the GABAergic interneuron cholinergic receptors. b–c, in the presence of a stimulus the amount of ACh released by the TANs decreases. If ACh is released in the matrix, the high AChE content of this milieu might stop the ACh signal very rapidly at the synaptic cleft, thereby avoiding nicotinic receptor activation on the GABAergic interneurons, and, therefore, facilitating the discharge of projection neurons. If the ACh release is inside a striosome, its low AChE content could facilitate activation of the nicotinic and muscarinic receptors on the GABAergic neurons, which, in turn, would inhibit the projection neurons. ACh, acetylcholine; AChE, acetylcholinesterase; ChAT-IN, cholinergic interneuron; GABA-IN, GABAergic interneuron; GP, globus pallidus; M, muscarinic receptor; N, nicotinic receptor; PN, projection neuron; SNr, substantia nigra pars reticulata.