Effect of l-cysteine on acetaldehyde self-administration
Alcohol. 2012-08-01; 46(5): 489-497
DOI: 10.1016/j.alcohol.2011.10.004
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Acetaldehyde (ACD), the first metabolite of ethanol, has been implicated in
several behavioural actions of alcohol, including its reinforcing effects.
Recently, we reported that l-cysteine, a sequestrating agent of ACD, reduced oral
ethanol self-administration and that ACD was orally self-administered. This study
examined the effects of l-cysteine pre-treatment during the acquisition and
maintenance phases of ACD (0.2%) self-administration as well as on the
deprivation effect after ACD extinction and on a progressive ratio (PR) schedule
of reinforcement. In a separate PR schedule of reinforcement, the effect of
l-cysteine was assessed on the break-point produced by ethanol (10%).
Furthermore, we tested the effect of l-cysteine on saccharin (0.2%)
reinforcement. Wistar rats were trained to self-administer ACD by nose poking on
a fixed ratio (FR1) schedule in 30-min daily sessions. Responses on an active
nose-poke caused delivery of ACD solution, whereas responses on an inactive
nose-poke had no consequences. l-cysteine reduced the acquisition (40 mg/kg), the
maintenance and the deprivation effect (100 mg/kg) of ACD self-administration.
Furthermore, at the same dose, l-cysteine (120 mg/kg) decreased both ACD and
ethanol break point. In addition, l-cysteine was unable to suppress the different
responses for saccharin, suggesting that its effect did not relate to an
unspecific decrease in a general motivational state. Compared to saline,
l-cysteine did not modify responses on inactive nose-pokes, suggesting an absence
of a non-specific behavioural activation. Taken together, these results could
support the hypotheses that ACD possesses reinforcing properties and l-cysteine
reduces motivation to self-administer ACD.