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Effects of morphine and methadone treatments on glutamatergic transmission in rat frontal cortex

Bartosz Bobula1, Grzegorz Hess

  • 1Department of Physiology, Institute of Pharmacology, Polish Academy of Sciences, Smetna 12, PL 31-343 Kraków, Poland.

Pharmacological Reports : PR
|January 19, 2010
PubMed

Insights

Repeated morphine, but not methadone, pretreatment specifically reduced cortical glutamatergic transmission. A subsequent morphine challenge dose further decreased AMPA/kainate and NMDA receptor activity in rat brain slices.

Area of Science:

  • Neuroscience
  • Pharmacology
  • Neurochemistry

Background:

  • Opioid analgesics like morphine and methadone are widely used.
  • Understanding their long-term effects on brain function is crucial.
  • Glutamatergic neurotransmission plays a key role in brain activity.

Purpose of the Study:

  • To investigate the specific effects of repeated morphine or methadone administration on cortical glutamatergic transmission.
  • To examine the impact of challenge doses of these opioids after repeated pretreatment.

Main Methods:

  • Ex vivo electrophysiological recordings from rat frontal cortical slices.
  • Repeated administration of morphine (10 mg/kg) or methadone (2.5 mg/kg) for seven days.
  • Challenge doses of morphine (5 mg/kg) or methadone (2.5 mg/kg) administered after a 14-day washout period.

Main Results:

  • Repeated morphine pretreatment followed by a morphine challenge significantly decreased both AMPA/kainate and NMDA components of evoked field potentials.
  • This specific effect was not observed when a methadone challenge was used after morphine pretreatment.
  • Neither morphine nor methadone challenge doses affected these glutamatergic components after repeated methadone pretreatment.

Conclusions:

  • Repeated morphine administration followed by a morphine challenge specifically alters cortical glutamatergic transmission.
  • Methadone does not produce the same specific alterations in cortical glutamatergic transmission.
  • These findings highlight differential neurochemical effects of chronic morphine and methadone exposure.

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