Abstract:

The striatum is the principal input nuclei to the BG and the DA through direct action of the nigrostriatal system on striatal synapses, selects and modulates learned motor programs. Modulatory actions of DA on Medium Spiny Neurons (MSNs) are very well described in relation to corticostriatal connection and glutamatergic release. Even the importance of cortical influences on MSN, there are other neuronal subtypes inside of the striatum, which establish connection with MSN and form the local circuits. GABAergic synaptic inputs to MSNs come from axonal collaterals of other MSNs, as well as, from interneurons, this synaptic influences shape MSNs activity, and both are modulated by DA. We have recently published that the net modulatory effect of DA on inhibitory synapses that GABAergic interneuron’s made on MSNs, is a decrease in the amplitude of the inhibitory postsynaptic current (IPSC). However the long term plasticity induced in this synapses (GABAergic interneuron’s-MSNs) depends on the DA concentration in addition to the activation of D1 or D2 receptors subtype. High Frequency Stimulation (HFS) in low DA concentration (200 nM) produced mostly LTD, whereas high concentration of DA (20 µM) favored the generation of LTP.