| Abstract: | A mechanism of the influence of dopamine-evoked modulation of lateral inhibition in the striatum on a conditioned selection of motor activity is proposed. According to suggested modulation rules for inhibitory transmission, action of dopamine on postsynaptic D1 (D2) receptors on striatonigral (striatopallidal) cells promotes long-term depression (potentiation) of inhibitory inputs simultaneously with potentiation (depression) of "strong" excitatory inputs that open NMDA channels on these neurons. If excitatory inputs are "weak" and NMDA channels are closed, modulation rules have opposite signs. Activation of presynaptic D2 (D1) receptors results in a decrease (increase) in GABA release from striatopallidal (striatonigral) axon terminals that innervate striatonigral (striatopallidal) cells. Thereof, dopamine-evoked modulation of lateral inhibition simultaneously strengthens both potentiation (depression) of excitatory inputs to "strongly" activated striatonigral (striatopallidal) neurons rising (reducing) their activity, and depression (potentiation) of excitatory inputs to "weakly" activated striatonigral (striatopallidal) neurons reducing (rising) their activity. Subsequent reorganization of neuronal activity in the cortico-basal-ganglia-thalamocortical loop promotes a conditioned selection of motor reaction because of the further increase (decrease) in activity of those motocortical neurons that "strongly" ("weakly") activated the striatum during dopamine release in response to conditioned stimulus. |
