Abstract
Rationale
Sardinian alcohol-preferring (sP) rats displayed high sensitivity to time schedule and consumed intoxicating amounts of alcohol during the last portion of the dark phase of the light/dark cycle when exposed to daily drinking sessions of 1 h, with concurrent availability of multiple alcohol concentrations and unpredictability of time of alcohol access.
Objectives
The present study investigated whether sensitivity of sP rats to time schedule extended to operant procedures of alcohol self-administration.
Methods
In experiment 1, three different alcohol solutions (10, 20, and 30 %, v/v) were concurrently available under a fixed ratio 4 schedule of reinforcement and with unpredictable time schedule; water was available uncontingently. Experiments 2 and 3 assessed the sensitivity of the motivational properties of alcohol to time schedule; rats were exposed to (a) self-administration sessions under the progressive ratio (PR) schedule of reinforcement and (b) sessions of alcohol seeking under the extinction responding (ER) schedule.
Results
In experiment 1, number of lever responses and amount of self-administered alcohol were positively correlated with time of alcohol access during the dark phase. When the self-administration session occurred at the first and latest hours of the dark phase, the amount of self-administered alcohol averaged 0.95–1.0 and 1.55–1.65 g/kg, respectively. In experiments 2 and 3, values of breakpoint and ER for alcohol were approximately 50 % higher when the sessions occurred at the last than first hour of the dark phase.
Conclusions
The reinforcing and motivational properties of alcohol were sensitive to time schedule and stronger at the end of the dark phase.
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Acknowledgments
The authors are grateful to Mrs. Carla Acciaro for animal breeding and care and Ms. Anne Farmer for language editing of the manuscript. Supported by NIAAA-funded “Integrative Neuroscience Initiative on Alcoholism” (INIA-Stress) Consortium.
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The authors declare that they have no competing interest.
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Maccioni, P., Lorrai, I., Marras, M.F. et al. Elevated reinforcing and motivational properties of alcohol at the end of the nocturnal period in sP rats. Psychopharmacology 232, 3585–3595 (2015). https://doi.org/10.1007/s00213-015-4010-2
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DOI: https://doi.org/10.1007/s00213-015-4010-2