Genetic Studies of Acute Tolerance, Rapid Tolerance, and Drinking in the Dark in the LXS Recombinant Inbred Strains

Abstract

Background We hypothesized that rapid tolerance (one-day tolerance) for the duration of the loss of righting reflex (“sleep time”; ST) was mediated by an increase in AFT. We also hypothesized that increased AFT would correspond to increased drinking. These questions were addressed using the LXS RI panel. Methods Mice were given a pretreatment dose of either saline or 5 g/kg alcohol on day one. On day two, mice were tested for ST (4.1 g/kg) using a method with which it is possible to accurately assess AFT. Genetic correlation analysis was conducted among the ST-related variables and also with “drinking in the dark” (DID) which was previously measured by Saba et al. (2011). Results Saline pretreated mice showed a continuous distribution of ST ranging from ~40 minutes to over 3 hours. Out of the 43 strains tested, 9 showed significantly decreased ST after alcohol pretreatment while in 3 strains, ST was significantly increased. AFT scores ranged from 0 to over 200 mg% in the saline group and in the alcohol group, 8 strains showed a significant increase in AFT and 2 strains showed significant decrease in AFT. In the saline group, AFT was significantly correlated to ST (r = −0.47), but not in the alcohol group (r = −0.22). DID was significantly correlated to only AFT in the alcohol pretreated group (r = 0.64). Conclusions The results suggest that AFT is an important component of the overall ST response, but that the alcohol pretreatment-induced change in AFT does not contribute to rapid ST tolerance. The significant correlation between DID and AFT in the alcohol group suggests that AFT may be a more relevant predictor of drinking behavior than the static measurement of ST. Moreover, pre-exposure to alcohol seems to change AFT in a way that makes it an even stronger predictor of drinking behavior.

Quantitative Trait Locus Mapping of Acute Functional Tolerance in the LXS Recombinant Inbred Strains

“…Importantly, a significant genetic correlation was found between drinking in the dark (DID), a model of binge drinking, and AFT in the alcohol‐pretreated mice, but not in the saline‐pretreated group. The correlation was in the predicted direction and was consistent with human studies; that is, higher drinking strains tended to have higher AFT (Radcliffe et al., ). This observation suggests that one's initial AFT may be less important to risk for pathological drinking behavior than the way it changes in response to prior experience with alcohol.…”

“…An average of 12 mice per strain and pretreatment condition (range: 3 to 18) was obtained resulting in 57 strains for ST_sal, 59 for ST_Et, 57 for AFT_sal, 59 for AFT_Et, and 57 for RT. Many of the mice (63%) were used in our previous study (Radcliffe et al., ). We have since tested an additional 535 mice which resulted in an increased n for 37 of the 44 original strains and in the addition of 15 new strains.…”

“…The concept of AFT is first credited to Mellanby () who observed that dogs that had been administered alcohol were more ataxic on the rising limb of alcohol distribution than they were at the same blood ethanol concentration (BEC) on the falling limb indicating the development of AFT. AFT has been shown to occur in humans as well as in rodents and also that it has an important genetic component (Cromer et al., ; Erwin and Deitrich, ; Hu et al., ; Radcliffe et al., , ). Thus, differences in LR and its association with AUDs may be due in part to genetic differences in AFT.…”

“…We have been investigating the genetics of AFT with the LXS using a procedure in which mice were administered a pretreatment of alcohol or saline 24 hours before being tested using the modified method of Ponomarev and Crabbe (). This procedure was originally employed to investigate rapid (1‐day) tolerance, and we subsequently discovered that the pretreatment altered AFT in a genotype‐dependent manner (Radcliffe et al., ; for further discussion of the relationship between AFT and RT, see Radcliffe et al., ). Importantly, a significant genetic correlation was found between drinking in the dark (DID), a model of binge drinking, and AFT in the alcohol‐pretreated mice, but not in the saline‐pretreated group.…”

Genome characterization of the selected long- and short-sleep mouse lines

“…AFT, first noted by Mellanby (1919), is the development of alcohol tolerance within a drinking session and it is thought to be a critical factor in the relationship between acute sensitivity and alcoholism risk noted above, although this relationship has not been firmly established (Bujarski et al 2015; Fillmore and Weafer 2012; King et al 2014; Newlin and Thomson 1990). More recently, with the use of the LXS RI panel, we showed a highly significant genetic correlation between AFT and drinking behavior and also mapped a significant QTL for AFT on distal chromosome 4 where others have also mapped QTLs for drinking behavior (Belknap and Atkins 2001; Bennett et al 2015; Radcliffe et al 2013; Saba et al 2011). In addition to our AFT mapping study, sleep time has been mapped in the LXS (Bennett et al 2006) and they also have been used for genetic analysis of a wide variety of alcohol and non-alcohol-related traits such as low-dose alcohol activation (Downing et al 2006), alcohol drinking (Saba et al 2011), hearing loss (Noben-Trauth et al 2010), dietary restriction-mediated lifespan (Rikke et al 2010), and body weight (Bennett et al 2005).…”