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Paradoxical Effect of NMDA Receptor Blockade in Chicks on Learning and Memory in Passive Avoidance Model
A A Tiunova1, N V Komissarova2, D V Bezryadnov2
1P. K. Anokhin Research Institute of Normal Physiology, Moscow, Russia. aat699@yahoo.com.
Abstract:
Activity of NMDA receptors is a prerequisite for numerous but not all forms of neuronal plasticity and learning. The present study examined the role of NMDA receptors in standard, weak, and repeated passive avoidance training in young chicks. Injection of MK-801, an antagonist of NMDA receptor, prior to strong training episode impaired subsequent memory recall. Moreover, repeated training did not restore the lost memory. In the double weak training protocol, the impairing effect of MK-801 was observed only when it was injected prior to the second but not to the first training episode. These results suggest that activation of NMDA receptors is not a necessary stage for memory acquisition in the weak training task. In contrast, the mechanisms of strong training depending on activation of NMDA receptors can be probably involved into the second training episode performed against the background of existing NMDA receptor-independent memory about the first training episode.
Insights
NMDA receptor activity is crucial for strong memory formation but not essential for initial weak learning. Repeated training doesn't recover NMDA receptor-dependent memories, highlighting distinct plasticity mechanisms.
Area of Science:
- Neuroscience
- Cognitive Science
- Learning and Memory
Background:
- NMDA receptors are vital for many forms of neuronal plasticity and learning.
- However, their necessity in all learning paradigms is not fully established.
Purpose of the Study:
- To investigate the role of NMDA receptors in different intensities and repetitions of passive avoidance training in young chicks.
- To determine if NMDA receptor activation is a prerequisite for memory acquisition across varying learning conditions.
Main Methods:
- Young chicks were subjected to standard, weak, and repeated passive avoidance training.
- MK-801, an NMDA receptor antagonist, was administered before training sessions.
- Memory recall was assessed after training to evaluate the impact of NMDA receptor blockade.
Main Results:
- MK-801 administration before strong training impaired memory recall.
- Repeated training failed to restore memory lost due to NMDA receptor antagonism.
- In weak training, MK-801 only impaired memory when given before the second training session, not the first.
Conclusions:
- NMDA receptor activation is not required for initial memory acquisition in weak training tasks.
- Strong training protocols rely on NMDA receptor activation, particularly during subsequent training sessions built upon prior NMDA receptor-independent memory.
