Morphine effects on mouse locomotor/exploratory activity: test dependency, test reliability, uni- and multi-variate...

Area of Science:

• Neurobehavioral toxicology
• Pharmacology
• Animal behavior studies

Background:

• Drug effects on animal activity are variable.
• Assessing drug effects requires standardized methods.
• Neurobehavioral toxicology uses drugs as probes.

Purpose of the Study:

• Compare morphine effects on mouse activity using three testing methods.
• Evaluate the impact of repeated drug exposure.
• Determine the most accurate method for assessing drug-induced behavioral changes.

Main Methods:

• CD-1 mice received morphine hydrochloride (0-100 mg/kg) via intraperitoneal injection.
• Behavioral activity was assessed using Varimex apparatus, toggle floor box, and videorecording.
• Tests were conducted twice, 24 hours apart, over 30-minute sessions.

Main Results:

• Morphine showed variable effects across tests: depression in Varimex, hyperactivity in toggle floor box.
• Videorecording revealed dose-dependent decreases in rearing and grooming, and increased crossing.
• No significant differences were observed between the first and second test sessions.

Conclusions:

• Videorecording provides a more accurate assessment of drug-induced locomotor and exploratory activity changes.
• Morphine's effects differ based on the testing apparatus.
• Repeated exposure did not alter morphine's behavioral effects in this study.