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Discriminative Stimulus Effects of Naltrexone and Haloperidol in Rats with Chronic, Intermittent Access to Sucrose
Author(s) -
Marek Morgan,
Moline Adam,
Altendorf Luke,
Vogelsang Jenna,
Cyra Matthew,
James Kimberly,
Herrmann Jody,
Levine Allen,
Jewett David
Publication year - 2017
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.31.1_supplement.1059.2
Subject(s) - naltrexone , haloperidol , saline , psychology , stimulus (psychology) , stimulus control , dopamine antagonist , anesthesia , pharmacology , medicine , antagonist , endocrinology , dopamine , receptor , psychotherapist , nicotine
Previous research demonstrated chronic, intermittent sucrose access increased endorphin and dopamine function, and naltrexone elicited some withdrawal‐like behaviors in rats. We determined the naltrexone serves as a discriminative stimulus (3.2 mg/kg, s.c.) in subjects with 12 hr access to sucrose (10–32%) followed by 12 hr access to water, but not in subjects with 24 hr access to water. We wondered if smaller naltrexone doses could be established as discriminative stimuli. Groups of rats were injected with naltrexone (0.1–1.0 mg/kg) or saline 1 hr after sucrose access and 15 min prior to discrimination training. Left lever presses were reinforced under a FR 15 schedule following drug administration, and right lever presses were reinforced following saline administration. Daily training session continued until rats emitted 80% or greater condition‐appropriate responses both prior to the first consequence and for the total session. Most subjects trained with either 0.32 or 1.0 mg/kg acquired the discrimination. Naltrexone (0.1 mg/kg) served as a discriminative stimulus in approximately one‐third of the subjects. We also attempted to establish the dopamine antagonist haloperidol as a discriminative stimulus. Haloperidol (0.056 mg/kg, 30 min PT) was established as a discriminative stimulus in 4 of 4 subjects with chronic, intermittent sucrose access (M=49 sessions) and 5 of 6 subjects with 24 hr water access (M=82 sessions). Two of 5 subjects with chronic, intermittent sucrose access discriminated haloperidol (0.018 mg/kg) from saline (M=84 sessions). Other subjects failed to acquire the discrimination in 120 sessions under these conditions. Haloperidol (0.056 mg/kg) significantly reduced rates of lever pressing. This effect of haloperidol was independent of liquid consumption. In sum, chronic sucrose consumption alters opioid function, naltrexone's ability to serve as a discriminative stimulus depends on the training dose, and sucrose consumption does not consistently alter the ability of haloperidol to serve as a discriminative stimulus. Support or Funding Information The University of Wisconsin‐Eau Claire Office of Research and Sponsored Programs and the Minnesota Obesity Center