Repeated stress increases locomotor response to amphetamine.

Area of Science:

• Neuroscience
• Behavioral Science
• Pharmacology

Background:

• Stress exposure can alter neurochemical systems.
• Dopamine pathways are implicated in locomotor activity and stress responses.
• Understanding stress-induced neuroplasticity is crucial for mental health research.

Purpose of the Study:

• To investigate the long-term effects of mild stress on locomotor responses to dopaminergic agents in rats.
• To determine the role of noradrenergic and dopaminergic systems in stress-induced behavioral changes.

Main Methods:

• Adult male rats were subjected to daily 20-minute electric foot shocks for 10 days.
• Locomotor activity was assessed 24 hours after the final shock session following administration of (+)amphetamine or apomorphine.
• Experiments included rats with surgically removed forebrain noradrenergic innervation.

Main Results:

• Stressed rats showed an enhanced locomotor response to (+)amphetamine compared to controls.
• This enhanced response persisted even after noradrenergic denervation, implicating dopamine.
• Stressed rats exhibited increased locomotor hyperactivity with a high dose of apomorphine, but similar hypoactivity with a low dose, suggesting increased postsynaptic dopamine sensitivity.

Conclusions:

• Repeated mild stress can lead to lasting alterations in dopaminergic system function, specifically increasing postsynaptic dopamine sensitivity.
• The observed behavioral changes are not due to permanent alterations in basal dopamine turnover.
• These findings highlight the complex interplay between stress, dopamine, and locomotor behavior.