Stress and Ketamine, Bimodal Influence on Cognitive Functions

Area of Science:

• Neuroscience
• Pharmacology
• Behavioral Science

Background:

• Ketamine, a glutamate N-methyl-D-aspartate receptor (NMDAR) antagonist, is a rapid-acting antidepressant.
• Prolonged stress induces depression and cognitive impairment.
• Long-term cognitive effects of ketamine, especially in stressed individuals, are not well understood.

Purpose of the Study:

• To investigate the long-term effects of ketamine on cognitive functions in rats exposed to chronic stress.
• To determine if prolonged ketamine administration can alleviate stress-induced memory deficits.

Main Methods:

• Rats were subjected to daily restraint stress for 21 days.
• Both stressed and non-stressed rats received daily ketamine treatment for 21 days.
• Cognitive functions were assessed using the Morris water maze (MWM), Barnes maze (BM), stereotypy test, open field test, and elevated plus maze (EPM).

Main Results:

• Ketamine induced significant stereotyped behavior.
• Stressed rats showed impaired spatial working and reference memory.
• In the MWM, ketamine improved memory in stressed rats but impaired it in non-stressed rats. In the BM, ketamine's effect varied over time in stressed rats.
• Ketamine did not significantly affect locomotor activity or anxiety levels.

Conclusions:

• Ketamine can prevent certain stress-induced memory impairments in rats.
• However, prolonged ketamine use may worsen memory deficits in non-stressed animals.
• The findings suggest potential therapeutic benefits of prolonged ketamine for stress-induced memory decline, but with caveats for cognitive function in unstressed individuals.