Volume 9, Issue 1 (Spring 2007)
Advances in Cognitive Sciences 2007, 9(1): 1-9 |
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1- Faculty of Biology, College of Science, University of Tehran, Tehran, Iran.
Abstract: (2721 Views)
Objective: In the present study, the effects of bilateral injections of N-methyl-D-aspartate (NMDA) receptor agonist and/or antagonist into the central amygdala (CeA) on the acquisition and expression of morphine induced conditioned place preference were investigated in male Wista rats.
Method: Male Wistar rats (240-280g) were used in this research. The cannulas were implanted (bilaterally) in the (CeA) by stereotaxic instrument. All animals were allowed 1 week to recover before CPP. Unbiased CPP was induced using a. 5-day schedule consisted of pre-conditioning, conditioning and testing phases.
Results: Animals that had received 3 daily subcutaneous (S.C.) injections of morphine (1-9mg/kg) or saline (1ml/kg) showed a significant preference for compartment paired with morphine in a dose dependent manner. Intra-CeA administration of the NMDA (0.01, 0.1 and 1mg/rat) with an ineffective dose of morphine (1mg/kg, S.C.) elicited a significant CPP. Administration of the non-competitive NMDA receptor antagonist, MK-801 (0.1, 0.3 and 0.5mg/rat) into the central amygdala inhibited the morphine (6mg/kg, s.c.)-induced place preference in a dose dependent manner. Furthermore, intra-CeA administration of MK-801 (0.25, 0.5 and 1mg/rat) reduced the response induced by NMDA (1mg/rat, intra-CeA) plus morphine (1mg/kg, s.c.). Neither NMDA nor MK-801 alone did produce a significant place preference or place aversion. Moreover, intra-CeA injection of NMDA but not MK-801 before testing significantly increased the expression of morphine (6mg/kg, s.c.)-induced place preference.
Conclusion: These results suggest that the glutamatergic system through the NMDA receptor mechanisms in the central amygdala may play an important role in the acquisition and expression of morphine-induced place preference.
Method: Male Wistar rats (240-280g) were used in this research. The cannulas were implanted (bilaterally) in the (CeA) by stereotaxic instrument. All animals were allowed 1 week to recover before CPP. Unbiased CPP was induced using a. 5-day schedule consisted of pre-conditioning, conditioning and testing phases.
Results: Animals that had received 3 daily subcutaneous (S.C.) injections of morphine (1-9mg/kg) or saline (1ml/kg) showed a significant preference for compartment paired with morphine in a dose dependent manner. Intra-CeA administration of the NMDA (0.01, 0.1 and 1mg/rat) with an ineffective dose of morphine (1mg/kg, S.C.) elicited a significant CPP. Administration of the non-competitive NMDA receptor antagonist, MK-801 (0.1, 0.3 and 0.5mg/rat) into the central amygdala inhibited the morphine (6mg/kg, s.c.)-induced place preference in a dose dependent manner. Furthermore, intra-CeA administration of MK-801 (0.25, 0.5 and 1mg/rat) reduced the response induced by NMDA (1mg/rat, intra-CeA) plus morphine (1mg/kg, s.c.). Neither NMDA nor MK-801 alone did produce a significant place preference or place aversion. Moreover, intra-CeA injection of NMDA but not MK-801 before testing significantly increased the expression of morphine (6mg/kg, s.c.)-induced place preference.
Conclusion: These results suggest that the glutamatergic system through the NMDA receptor mechanisms in the central amygdala may play an important role in the acquisition and expression of morphine-induced place preference.
Type of Study: Research |
Subject:
Special
Received: 2006/09/24 | Accepted: 2007/01/18 | Published: 2007/03/21
Received: 2006/09/24 | Accepted: 2007/01/18 | Published: 2007/03/21
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