Changes in mu opiate receptors following inescapable shock

Area of Science:

• Neuroscience
• Behavioral Science
• Pharmacology

Background:

• Inescapable shock induces hypoalgesia (reduced pain sensitivity) in rats.
• Endogenous opiate system activity is implicated in stress-induced hypoalgesia.

Purpose of the Study:

• To investigate the effect of inescapable shock on mu-opiate receptor binding in rat brains.
• To determine if changes in receptor number or affinity underlie altered opiate activity.

Main Methods:

• Rats were exposed to no shock, inescapable shock, or escapable shock.
• Binding of [3H]DAGO, a selective mu-opiate receptor agonist, was measured in brain tissue.
• Analysis focused on midbrain regions.

Main Results:

• A significant decrease in [3H]DAGO binding was observed in the midbrains of rats exposed to inescapable shock compared to control groups.
• This reduction in binding was attributed to a decrease in the number of mu-opiate receptors, not a change in their binding affinity.

Conclusions:

• Inescapable shock exposure leads to long-term alterations in the endogenous opiate system.
• Reduced mu-opiate receptor availability in the midbrain may contribute to the hypoalgesic effects of inescapable stress.