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The biphasic effect of morphine on odor conditioning in neonatal rats
Author(s) -
Randall Christopher K.,
Kraemer Philipp J.,
Dose John M.,
Carbary Timothy J.,
Bardo Michael T.
Publication year - 1992
Publication title -
developmental psychobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.055
H-Index - 93
eISSN - 1098-2302
pISSN - 0012-1630
DOI - 10.1002/dev.420250506
Subject(s) - odor , morphine , conditioning , chemistry , opioid , medicine , anesthesia , endocrinology , biochemistry , receptor , statistics , mathematics , organic chemistry
Three experiments examined the dose‐dependent biphasic effect of morphine on odor conditioning in neonatal rats. In Experiment 1, a single pairing of an odor and a low dose of morphine (0.5 mg/kg) in 5‐day‐old rats produced an odor preference, relative to an unpaired control group. In Experiment 2, pairing an odor with a high dose of morphine (2.0 mg/kg) produced an odor aversion, relative to an unpaired control group. A third experiment compared performance of a group given odor and morphine (2.0 mg/kg) paired to that of two unpaired groups: one given morphine 24 hr prior to and the other 24 hr after odor exposure. The paired group showed an odor aversion relative to both of the unpaired groups, which did not differ. The latter finding suggests that even if morphine metabolism is incomplete after 24 hr, behavior is unaffected. These results are discussed in reference to the functional development of the opioid system in rats © 1992 John Wiley & Sons, Inc.