Stress-induced sensitization and facilitated learning require NMDA receptor activation

Area of Science:

• Neuroscience
• Behavioral Neuroscience
• Neuropharmacology

Background:

• Inescapable stress can facilitate classical conditioning, such as the eyeblink response in rats.
• The precise neurobiological mechanisms underlying stress-induced learning facilitation remain under investigation.

Purpose of the Study:

• To test the hypothesis that N-methyl-D-aspartate (NMDA) receptor activation mediates stress-induced facilitation of classical eyeblink conditioning.
• To explore the role of NMDA receptors in stress-related learning enhancement.

Main Methods:

• Rats received injections of an NMDA receptor antagonist (CGP-37849) or vehicle.
• Following injection, rats were exposed to an inescapable stressor (restraint and tail shocks).
• Classical eyeblink conditioning was assessed 24 hours later.

Main Results:

• Rats treated with vehicle showed significant facilitation of conditioned eyeblink response after stress exposure.
• Rats treated with the NMDA antagonist CGP-37849 during stress exposure did not show this facilitation.
• The NMDA antagonist alone did not impair learning.

Conclusions:

• Stress-induced facilitation of classical conditioning is dependent on NMDA receptor activation.
• These findings support the hypothesis that stress enhances learning through mechanisms similar to long-term potentiation (LTP).