Related Experiment Videos
Effects of methadone on activity and on brain monoamines in two strains of mice
Abstract:
Two strains of mice (C57BL/6J and DBA/2J) were used to determine the effects of single and multiple injections of methadone on open field activity and on brain monoamines. For the DBA strain, the initial injection of methadone produced an attenuation of locomotor activity. After 7 daily injections, activity increased to that of controls. For the C57 strain, the initial injection produced a slight increase in activity which became more pronounced after further daily injections. Norepinephrine concentration was elevated in brains of DBA mice chronically exposed to methadone. This effect was not observed in C57 mice nor in either strain injected only once with the drug. Serotonin concentration was not altered in animals of either strain whether acutely or chronically exposed to methadone. The results of this study suggest: 1) that activity change following methadone injections is dependent upon genetic factors and previous experience with the drug; 2) that the tolerance develops to the drug produced decreases but not increases in activity; and 3) that chronic exposure to the drug can elevate norepinephrine concentration in the brains of DBA mice.
Insights
Methadone affects mouse activity and brain chemistry differently based on genetics and prior exposure. Chronic methadone use in DBA mice elevated norepinephrine levels, but not serotonin.
Area of Science:
- Neuropharmacology
- Behavioral Neuroscience
- Genetics
Background:
- Methadone is an opioid agonist used for pain management and opioid use disorder treatment.
- Its effects on behavior and neurochemistry can vary significantly.
- Understanding these variations is crucial for optimizing therapeutic use and managing side effects.
Purpose of the Study:
- To investigate the impact of single and multiple methadone injections on locomotor activity.
- To analyze the effects of methadone on brain monoamine levels (norepinephrine and serotonin).
- To explore strain-specific and experience-dependent responses to methadone in mice.
Main Methods:
- Two mouse strains, C57BL/6J and DBA/2J, were used.
- Mice received single or daily injections of methadone for seven days.
- Open field activity was monitored, and brain monoamine concentrations were measured.
Main Results:
- DBA mice showed decreased activity after initial methadone injection, returning to control levels after chronic exposure.
- C57 mice exhibited increased activity, which became more pronounced with repeated injections.
- Chronic methadone elevated norepinephrine in DBA mice's brains; serotonin levels remained unchanged in both strains.
Conclusions:
- Methadone's effects on locomotor activity are influenced by genetic background and prior drug exposure.
- Tolerance develops to methadone's activity-decreasing effects but not its increasing effects.
- Chronic methadone administration can lead to elevated brain norepinephrine levels in specific mouse strains (DBA/2J).