Stress-induced dynamic changes in mouse brain polyamines. Role in behavioral reactivity

Area of Science:

• Neuroscience
• Biochemistry
• Stress Physiology

Background:

• Rapid, transient changes in brain polyamine metabolism, termed the polyamine-stress-response, are observed after chronic intermittent stress.
• Polyamines are crucial for cellular functions, and their dysregulation is implicated in various neurological conditions.

Purpose of the Study:

• To investigate the effects of chronic intermittent restraint stress and dexamethasone on hippocampal polyamine concentrations in mice.
• To examine the impact of alpha-difluoromethylornithine (an ornithine decarboxylase inhibitor) on stress-induced polyamine changes and behavioral reactivity.

Main Methods:

• Adult male C57BL/6 mice were subjected to chronic intermittent restraint stress or daily intraperitoneal dexamethasone injections.
• Polyamine concentrations (putrescine, spermidine, spermine) in the hippocampus were measured.
• Mice were treated with alpha-difluoromethylornithine and assessed for behavioral changes in an open-field arena.

Main Results:

• Chronic restraint stress led to transient increases in putrescine after each episode, with delayed increases in spermidine and spermine after specific episodes.
• Dexamethasone injections, similar to vehicle, increased all measured polyamine concentrations.
• Alpha-difluoromethylornithine treatment depleted putrescine, reduced overall polyamines, and altered open-field activity, suggesting modified emotional behavior.

Conclusions:

• The brain's polyamine-stress-response is dynamic, varying with stressor type, intensity, and duration.
• Dexamethasone may induce persistent alterations in polyamine levels, while alpha-difluoromethylornithine modulates both polyamine concentrations and emotional reactivity.
• The polyamine-stress-response is implicated as an adaptive mechanism in reacting to stressors.