An operant ethanol self-administration paradigm that discriminates between appetitive and consummatory behaviors reveals distinct behavioral phenotypes in commonly used rat strains

Variables affecting acquisition and maintenance of operant ethanol self-administration in male and female Long-Evans rats

“…showed that the amount of ethanol consumed in the home cage was not predictive of consumption in the operant setting (Patwell et al, 2021).…”

“…To determine the effect of prior experience drinking ethanol on the acquisition of operant ethanol self-administration, male rats were habituated to ethanol drinking in the home cage for three weeks prior to operant training. Rats assigned to the Water/Ethanol (W/E) group (n=24) underwent a standard intermittent-access two-bottle choice procedure identical to previously published procedures (Simms et al ., 2008; Patwell et al ., 2021). Rats were provided with one bottle of water and one bottle containing ethanol (20% v/v) in tap water on Mondays, Wednesdays, and Fridays approximately 30 min after the onset of the dark cycle.…”

“…Operant training was performed in lickometer-equipped operant boxes (Med Associates, St Albans, VT) using previously published methods (Patwell et al ., 2021). Rats were trained to self-administer either ethanol (20% v/v) or sucrose (1% w/v).…”

“…Surprisingly, however, these studies did not include comparisons to a group that was naïve to ethanol prior to operant training making it impossible to determine the advantage of this approach over one that trains rats to operantly self-administer in the absence of prior experience drinking ethanol. Importantly, recent data suggests that the level of ethanol intake during intermittent-access two-bottle choice home cage drinking is not predictive of intake during operant self-administration (Patwell et al ., 2021) adding further uncertainty to the benefit of this experimental approach.…”

“…Although exciting, it should be noted that both of these studies suggested that differences in drinking patterns contributed to changes in ethanol intake during operant sessions of shorter duration, yet, neither study used methods that incorporate direct measures of consumption. Use of such methods in studies of ethanol drinking patterns is crucial in light of work showing that a significant number of animals refrain from drinking ethanol despite completion of the operant response requirement (Blegen et al ., 2018; Patwell et al ., 2021). Thus, additional studies are needed, particularly those that measure consumption directly, in order to lend further support to this approach.…”