MK-801 induced retrieval, but not acquisition, deficits for passive avoidance conditioning

Area of Science:

• Neuroscience
• Behavioral Pharmacology
• Cognitive Psychology

Background:

• State-dependent retention (SDR) is a phenomenon where memory retrieval is enhanced when the internal state during retrieval matches the state during learning.
• MK-801 is an NMDA receptor antagonist with known effects on learning and memory.

Purpose of the Study:

• To investigate the effects of MK-801 on the acquisition and retention of avoidance responses in rats.
• To determine if MK-801 induces state-dependent retention for passive avoidance (PA) tasks.

Main Methods:

• Two experiments utilized a state-dependent retention (SDR) design with rats.
• Animals were trained on an avoidance task and tested after saline or MK-801 injections (0.05 and 0.10 mg/kg).
• Immediate and 24-h retention tests were conducted to assess learning and memory recall.

Main Results:

• MK-801 did not impair the acquisition of the avoidance response at either dose.
• A higher dose (0.10 mg/kg) of MK-801 rendered passive avoidance (PA) memory state-dependent.
• Data marginally supported SDR interpretation in Experiment 1, with clearer state-dependency shown in Experiment 2.

Conclusions:

• MK-801, at the tested doses, does not prevent the acquisition of avoidance responses.
• MK-801 can induce state-dependent retention for passive avoidance memory, suggesting its potential role as a cue state.
• Doses of MK-801 that do not impair PA learning can influence the expression of memory for PA training.