Morphine tolerance offers protection from radiogenic performance deficits

Area of Science:

• Neuroscience
• Radiation Biology
• Behavioral Science

Background:

• Ionizing radiation exposure in rats causes behavioral changes like lethargy and performance deficits.
• These radiation-induced behaviors resemble those seen after morphine administration in rats.
• Endogenous opiates are linked to stress responses, prompting investigation into their role in radiation effects.

Purpose of the Study:

• To investigate the potential role of endogenous opiates in radiation-induced behavioral deficits.
• To determine if morphine tolerance confers resistance to the behavioral effects of ionizing radiation.

Main Methods:

• Rats were trained on a signaled avoidance task.
• Subjects received either morphine or placebo implants to induce tolerance or control.
• Morphine tolerance was assessed via body temperature changes.
• Rats were exposed to 2500 rad 60Co radiation or sham irradiation.
• Behavioral performance on the avoidance task was retested 24 hours post-exposure.

Main Results:

• Morphine-tolerant rats showed significantly better performance after irradiation compared to irradiated placebo-implanted rats.
• Morphine-tolerant rats performed similarly to non-irradiated, morphine-tolerant controls.
• Morphine tolerance provided a degree of behavioral resistance to radiation exposure.

Conclusions:

• Morphine tolerance appears to mitigate behavioral deficits caused by ionizing radiation in rats.
• These findings support the hypothesis that excessive release of endogenous opiates contributes to radiation-induced behavioral impairments.