The object of the diagram is to show the interactions between the
ionic channels and the biochemical signalling in the spine of the
Medium Spiny Neuron of the Striatum. Constitutively, DARPP-32 forms a
complex with PP1 after been phosphorylated by PKA (grey line).
According to the concentration of Calcium two possible pathways can be
selected: when Calcium concentration is low the orange pathway is
selected, with the activation of Calcineurin and release of PP1 from
the DARPP-32 complex, with consequent dephosphorylation of AMPARs;
when the Calcium concentration is high, the yellow pathway is selected
with the complex CaMKII/Calmodulin able to phosphorylates the AMPARs.
In light blue is represented the Calcium flux incoming from the ionic
channels, AMPARs, NMDARs and Voltage Gated Calcium Channel (VGCC)s.

Michele Mattioni and Nicolas Le Novère
Computational Systems Neurobiology group
EMBL-EBI, Hinxton, UK.