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. Author manuscript; available in PMC: 2012 Apr 1.
Published in final edited form as: Curr Opin Neurobiol. 2011 Feb 16;21(2):322–327. doi: 10.1016/j.conb.2011.01.005

Figure 1. Regulation of synaptic plasticity and behavioral state by striatal neuromodulators.

Figure 1

Left, when the levels of dopamine are high relative to adenosine and acetylcholine, cAMP/PKA activity is low in indirect-pathway MSNs, biasing excitatory synapses onto those cells towards LTD. Meanwhile, cAMP/PKA activity is high in direct-pathway MSNs, biasing excitatory synapses onto those cells towards LTP. Indirect-pathway LTD and direct pathway LTP are proposed to cause an active, motivated behavioral state. Right, when the levels of dopamine are low relative to adenosine and acetylcholine, cAMP/PKA activity is high in indirect-pathway MSNs, biasing excitatory synapses onto those cells towards LTP. Meanwhile, cAMP/PKA activity is low in direct-pathway MSNs, biasing excitatory synapses onto those cells towards LTD. Indirect-pathway LTP and direct pathway LTD are proposed to induce an inactive, apathetic behavioral state.