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Updated: Aug 7, 2026
A General Method for Evaluating Deep Brain Stimulation Effects on Intravenous Methamphetamine Self-Administration
Published on: January 22, 2016
The effects of methadone on cortical and subcortical EEG in the rat
Abstract:
(1) Administration of methadone in rats elicited high voltage, slow activity in the cerebral cortex and low voltage irregular waves in the hippocampus. Intravenous administration of methadone (0.2-0.5 mg/kg) markedly increased the threshold for cortical desynchronization by stimulation of the MRF. This increase by methadone was dose dependent. (2) Cortical desynchronization following mechanical stimulation of the tail or foot was blocked by methadone at a dose level of 0.5 mg/kg. At this dose level, the cortical desynchronizing threshold for MRF stimulation increased more than 8-fold whereas the threshold for MT and DH stimulations showed only small but measurable increases. A minimum dose of 0.5 mg/kg was needed to raise the threshold of these structures significantly (3) The increased threshold following injection of methadone was completely blocked by prior injection of the antagonist naloxone, indicating this response to be specific. Naloxone alone had no effect on electrical activity at any site. (4) The incidence of dissociation of the cortical response from the limbic system response after stimulation of the dorsal hypothalamus was approximately 4 times greater in methadone-treated than in untreated animals.
Insights
Methadone increases brain activity thresholds, specifically blocking desynchronization from stimuli. This effect is dose-dependent and reversed by naloxone, confirming its opioid receptor specificity.
Area of Science:
- Neuroscience
- Pharmacology
Background:
- Methadone is an opioid agonist used for pain management and opioid addiction treatment.
- Its effects on brain electrical activity, particularly in response to stimuli, require further elucidation.
Purpose of the Study:
- To investigate the impact of methadone administration on electroencephalographic (EEG) activity in rats.
- To determine methadone's effect on the threshold for cortical desynchronization induced by various stimuli.
Main Methods:
- Intravenous administration of methadone (0.2-0.5 mg/kg) to rats.
- Stimulation of the midbrain reticular formation (MRF), mechanical stimulation of the tail/foot, and stimulation of the medial thalamus (MT) and dorsal hypothalamus (DH).
- Measurement of cortical desynchronization thresholds and EEG patterns in the cerebral cortex and hippocampus.
- Administration of naloxone as an opioid antagonist.
Main Results:
- Methadone dose-dependently increased the threshold for cortical desynchronization induced by MRF stimulation.
- A dose of 0.5 mg/kg methadone blocked cortical desynchronization from tail/foot stimulation and significantly increased thresholds for MRF, MT, and DH stimulation.
- Naloxone completely blocked methadone's effect on thresholds, indicating opioid receptor involvement.
- Methadone treatment increased the dissociation between cortical and limbic responses to dorsal hypothalamus stimulation.
Conclusions:
- Methadone exerts significant dose-dependent effects on brain electrical activity, increasing thresholds for desynchronization.
- These effects are mediated via opioid receptors and can alter sensory processing and limbic system integration.
