The role of glutamate NMDA receptors of the mediodorsal thalamus in scopolamine-induced amnesia in rats

The current study was designed to examine the role of glutamate NMDA receptors of the mediodorsal thalamus (MD) in scopolamine-induced memory impairment. Adult male rats were bilaterally cannulated into the MD. According to the results, intraperitoneal (i.p.) administration of scopolamine (1.5 mg/kg) immediately after the training phase (post-training) impaired memory consolidation. Bilateral microinjection of the glutamate NMDA receptors agonist, N-Methyl-D-aspartic acid (NMDA; 0.05 µg/rat), into the MD significantly improved scopolamine-induced memory consolidation impairment. Co-administration of D-AP5, a glutamate NMDA receptor antagonist (0.001-0.005 µg/rat, intra-MD) potentiated the response of an ineffective dose of scopolamine (0.5 mg/kg, i.p.) to impair memory consolidation, mimicking the response of a higher dose of scopolamine. Noteworthy, post-training intra-MD microinjections of the same doses of NMDA or D-AP5 alone had no effect on memory consolidation. Moreover, the blockade of the glutamate NMDA receptors by 0.003 ng/rat of D-AP5 prevented the improving effect of NMDA on scopolamine-induced amnesia. Thus, it can be concluded that the MD glutamatergic system may be involved in scopolamine-induced memory impairment via the NMDA receptor signaling pathway.

 

Comments:

This study delves into the role of glutamate NMDA receptors in the mediodorsal thalamus (MD) concerning scopolamine-induced memory impairment in rats. Here's a breakdown of the key findings:

1. **Scopolamine's Effect on Memory:** Administering scopolamine after the training phase impaired memory consolidation.

2. **NMDA Receptor Agonist (NMDA) and Memory:** Injecting the NMDA agonist directly into the MD improved scopolamine-induced memory consolidation impairment.

3. **Effect of NMDA or D-AP5 Alone:** Administering NMDA or D-AP5 alone into the MD post-training had no impact on memory consolidation.

4. **D-AP5 Potentiation of Scopolamine:** Co-administering D-AP5 with a lower dose of scopolamine potentiated its effect, mimicking the response of a higher dose of scopolamine in impairing memory consolidation.

5. **Blocking NMDA Receptors and Memory Improvement:** Blocking glutamate NMDA receptors with D-AP5 prevented the positive effect of NMDA on scopolamine-induced amnesia, indicating the involvement of the MD glutamatergic system in scopolamine-induced memory impairment through the NMDA receptor signaling pathway.

This suggests a complex interplay within the MD involving NMDA receptors, where activation or blockade could respectively improve or exacerbate scopolamine-induced memory impairment. This study sheds light on the potential of manipulating these receptors to modulate memory processes affected by scopolamine.

Related Products

Cat.No.	Product Name	Information
E1246	D-AP5	D-AP5 (D-APV; D-2-Amino-5-phosphonovaleric acid) is a selective and competitive NMDA receptor antagonist that inhibits the glutamate binding site of NMDA receptors.

Related Targets

NMDAR