Introduction: 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).
Discussion: It can be concluded that D1/D2-like receptors within this region have an important
role in morphine-seeking behaviors in extinguished rats.
Type of Study:
Original |
Subject:
Behavioral Neuroscience Received: 2014/08/6 | Accepted: 2015/02/18 | Published: 2015/04/1