Microdialysis reveals a morphine-induced increase in pallidal opioid peptide release.
Freely moving rats were implanted with microdialysis probes in the globus pallidus/ventral pallidum, nucleus accumbens or caudate nucleus. Morphine (10 mg kg-1 i.p.) induced an average 128% increase in extracellular opioid peptide levels in the pallidum over a 2 h period peaking 1 h after injection. No change was observed in the nucleus accumbens or caudate nucleus. Dose-response analysis showed a smaller (26%), non-significant, increase at a lower dose of 2 mg kg-1 and no effect at a higher dose of 40 mg kg-1. No evidence of significant acute tolerance was apparent following repeated administration of morphine (10 mg kg-1, i.p.) at 3 h intervals. The magnitude of the morphine effect varied greatly between animals and was dependent on the pre-injection baseline opioid peptide levels.
Olive
M F
MF
Department of Psychiatry & Biobehavioral Sciences, UCLA School of Medicine 90024-1759, USA.
Bertolucci
M
M
Evans
C J
CJ
Maidment
N T
NT
D000818:Animals; D004305:Dose-Response Relationship, Drug; D005917:Globus Pallidus / Q000187:drug effects* / Q000378:metabolism; D008297:Male; D017551:Microdialysis; D009020:Morphine / Q000494:pharmacology*; D009714:Nucleus Accumbens / Q000187:drug effects / Q000378:metabolism; D018847:Opioid Peptides / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013997:Time Factors
D018847:Opioid Peptides; D009020:Morphine