The Blockade of D1/D2-Like Dopamine Receptors within the Dentate Gyrus of Hippocampus Decreased the Reinstatement of Morphine-Extinguished Conditioned Place Preference in Rats.
BACKGROUND
The hippocampus (HIP), the primary brain structure related to learning and memory, receives sparse but comprehensive dopamine innervations and contains dopamine D1/D2-like receptors. It is demonstrated that dopamine receptors in dentate gyrus (DG) region of HIP have a remarkable function in spatial reward processing. Much less is known about the involvement of HIP and its D1/D2 dopamine receptors in drug-seeking behaviors, more particularly, in the morphine extinguished conditioned place preference (CPP).


METHODS
To find out the role of D1/D2-like receptors within the DG in morphine-seeking behaviors, forty adult male albino Wistar rats weighing 220-280g were unilaterally implanted by a cannula into the DG. The CPP paradigm was done; conditioning score and locomotors activity were recorded by Ethovision software. All drugs/vehicles were microinjected one day after extinction (just before the CPP test) into the DG as reinstatement day.


RESULTS
The results showed that intra-DG administration of different dose of SCH23390 (0.25, 1 and 4μg/0.5μl saline), as a selective D1-like receptor antagonist and sulpiride (0.25, 1 and 4μg/0.5μl DMSO), as a selective D2-like receptor antagonist dose-dependently attenuated the morphine-extinguished CPP reinstated by priming injection of morphine (1 mg/kg;sc).


CONCLUSIONS
It can be concluded that D1/D2-like receptors within this region have an important role in morphine-seeking behaviors in extinguished rats.
Cellular & Molecular Research Center and Department of Physiology, School of Medicine, Guilan University of Medical Sciences, Rasht, Iran.
Behrooz
B
Khakpour-Taleghani
Neuroscience Research Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
Zahra
Z
Reisi
Neuroscience Research Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
Abbas
A
Haghparast
D1-like receptor; D2-like receptor; Dentate gyrus; Morphine; Reinstatement; Reward