Figure 9. Schematic diagrams showing the synaptic organization of the NAc and the proposed mechanisms of action of CCK to decrease evoked EPSCs in the NAc.

A, CCK_B receptors are present mainly on intrinsic projection neurones which form extensive axon collateral networks exerting a powerful inhibitory effect on to neighbouring cells. The NAc receives excitatory inputs from limbic areas, e.g. prefrontal cortex, amygdala and hippocampus which have GABA_B receptors on their terminals. It also receives a dopaminergic input from the ventral tegmental area. CCK is colocalized with glutamate and DA in these afferent terminals. B, a schematic showing the possible mechanisms of action of CCK for depressing EPSC and the likely contributions of the different mechanisms to the CCK effect. The thickness of the arrows represents the postulated contributions of each pathway to the overall effect.