Effects of morphine and methadone treatments on glutamatergic transmission in rat frontal cortex.
The effects of repeated administration of morphine and methadone, followed by a challenge dose of either morphine or methadone were examined ex vivo in rat frontal cortical slices that were prepared 1 h after final drug administration. Morphine challenge dose (5 mg/kg), administered 14 days after the end of repeated morphine pretreatment (10 mg/kg, administered 7 times) decreased both the AMPA/kainate and the NMDA components of field potentials that were evoked in cortical layer II/III by electrical stimulation. This effect did not occur either when a methadone challenge dose (2.5 mg/kg) was administered instead of morphine or after repeated morphine treatment. Moreover, after repeated methadone treatment (2.5 mg/kg, administered 7 times), neither morphine nor methadone challenge affected AMPA/kainate or NMDA components of the field potentials. These data indicate a specific effect of repeated morphine followed by morphine challenge on cortical glutamatergic transmission.
Bobula
Bartosz
B
Department of Physiology, Institute of Pharmacology, Polish Academy of Sciences, Smetna 12, PL 31-343 Kraków, Poland.
Hess
Grzegorz
G
D000701:Analgesics, Opioid / Q000008:administration & dosage / Q000494:pharmacology*; D000818:Animals; D004305:Dose-Response Relationship, Drug; D004334:Drug Administration Schedule; D004558:Electric Stimulation; D005071:Evoked Potentials; D005625:Frontal Lobe / Q000187:drug effects / Q000378:metabolism; D008297:Male; D008691:Methadone / Q000008:administration & dosage / Q000494:pharmacology*; D009020:Morphine / Q000008:administration & dosage / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D018091:Receptors, AMPA / Q000187:drug effects / Q000378:metabolism; D018092:Kainic Acid Receptors / Q000187:drug effects / Q000378:metabolism; D016194:Receptors, N-Methyl-D-Aspartate / Q000187:drug effects / Q000378:metabolism
D000701:Analgesics, Opioid; D008691:Methadone; D009020:Morphine; D018091:Receptors, AMPA; D018092:Kainic Acid Receptors; D016194:Receptors, N-Methyl-D-Aspartate