Effects of endogenous morphine deprivation on memory retention of passive avoidance learning in mice.
Memory and the processes of learning in mammals are well known to be affected by opioid agonists such as morphine, which has been proven to interfere and cause amnesia. The presence of endogenous morphine has been demonstrated in various tissues from mammals to invertebrates. In this study, we have investigated the effects caused by in-vivo immunodepletion of endogenous morphine on working memory under different experimental conditions. When mice were submitted to fasting, a stress condition, acquisition and consolidation of memory were significantly impaired compared to controls. This was demonstrated by a decrease in entry latency into the dark room in the retention session of the passive avoidance test. This effect was significantly reversed to baseline values when endogenous morphine was depleted from the extracellular brain space. These findings support a role for endogenous morphine in weakening memory processes under stress conditions.
Department of Anatomical and Biomedical Sciences, University of Siena, Italy.
Massimo
M
Guarna
Carla
C
Ghelardini
Nicoletta
N
Galeotti
Alessandro
A
Bartolini
Laura
L
Noli
Carla
C
Neri
George B
GB
Stefano
Enrica
E
Bianchi
D000818:Animals; D019138:Antibodies, Blocking / Q000494:pharmacology; D001362:Avoidance Learning / Q000502:physiology*; D001923:Brain Chemistry / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D005110:Extracellular Space / Q000187:drug effects / Q000378:metabolism; D005215:Fasting / Q000502:physiology; D008401:Gas Chromatography-Mass Spectrometry; D007074:Immunoglobulin G / Q000494:pharmacology; D007276:Injections, Intraventricular; D008297:Male; D008568:Memory / Q000502:physiology*; D051379:Mice; D009020:Morphine / Q000494:pharmacology; D009043:Motor Activity / Q000187:drug effects; D009294:Narcotics / Q000494:pharmacology; D018847:Opioid Peptides / Q000037:antagonists & inhibitors*; D004856:Postural Balance / Q000187:drug effects; D011597:Psychomotor Performance / Q000187:drug effects; D013315:Stress, Psychological / Q000523:psychology
D019138:Antibodies, Blocking; D007074:Immunoglobulin G; D009294:Narcotics; D018847:Opioid Peptides; D009020:Morphine