Research reportRole of ventral pallidal D2 dopamine receptors in the consolidation of spatial memory

- D2 DA receptor agonist quinpirole was injected into the ventral pallidum (VP).
- Quinpirole enhances memory consolidation in spatial learning.
- Quinpirole increases stability of the formed memory against extinction.
- D2 DA receptor antagonist sulpiride pretreatment blocks the agonist's effect.
- Sulpiride in the VP induces spatial learning deficit.

The role of dopamine (DA) receptors in spatial memory consolidation has been demonstrated in numerous brain regions, among others in the nucleus accumbens which innervates the ventral pallidum (VP). The VP contains both D1 and D2 DA receptors. We have recently shown that the VP D1 DA receptor activation facilitates consolidation of spatial memory in Morris water maze test. In the present study, the role of VP D2 DA receptors was investigated in the same paradigm.In the first experiment, the D2 DA receptor agonist quinpirole was administered into the VP of male Wistar rats in three doses (0.1, 1.0 or 5.0 μg, respectively in 0.4 μl physiological saline). In the second experiment, the D2 DA receptor antagonist sulpiride was applied to elucidate whether it can antagonise the effects of quinpirole. The antagonist (4.0 μg, dissolved in 0.4 μl physiological saline) was microinjected into the VP either by itself or prior to 1.0 μg agonist treatment. Control animals received saline in both experiments.The two higher doses (1.0 and 5.0 μg) of the agonist accelerated memory consolidation relative to controls and increased the stability of the consolidated memory against extinction. Sulpiride pretreatment antagonised the effects of quinpirole. In addition, the antagonist microinjected into the VP immediately after the second conditioning trial impaired learning functions.The present data provide evidences for the important role of VP D2 DA receptors in the consolidation and stabilization of spatial memory.