Long-term exposure to daily ethanol injections in DBA/2J and Swiss mice: Lessons for the interpretation of ethanol sensitization

Abstract

Most mice ethanol sensitization studies focused on neurobiology at the expense of its behavioral characterization. Furthermore, relatively short ethanol exposures (10 to 20 injections) were used in these studies. The first aim of the present study is to better characterize the development and expression of ethanol sensitization after an extended exposure of 45 daily injections. In some previous studies, mice were classified as “respondent” and “resistant” to ethanol sensitization. The second aim of the present study is to test the long-term reliability of such categorizations and the consequences of their use on the interpretation of the ethanol sensitization results. Swiss and DBA/2J female mice received 45 consecutive daily ethanol administrations (respectively 2.5 and 2.0 g/kg) and their locomotor activity was daily recorded to test the development of ethanol sensitization. At the end of the procedure, a challenge test assessed the inter-group ethanol sensitization.The results of the present study show that ethanol sensitization continues to develop beyond 20 days to reach maximal levels after about 25 injections in DBA/2J mice and 40 injections in Swiss mice, although the core phase of the development of ethanol sensitization occurred in both strains during the first 20 days. Remarkably, ethanol sensitization after such a long daily ethanol treatment resulted in both an upward shift of the magnitude of ethanol stimulant effects and a prolongation of these effects in time (up to 30 minutes). Mice classified as “resistant to ethanol sensitization” according to previous studies developed very significant levels of ethanol sensitization when tested after 45 ethanol injections and are best described as showing a delayed development of ethanol sensitization. Furthermore, mice classified as respondent or resistant to ethanol sensitization also differ in their acute response to ethanol, such that it is difficult to ascertain whether these classifications are specifically related to the sensitization process.

Carbetocin Inhibits Behavioral Sensitization to Ethanol in Male and Female Mice, Independent of Corticosterone Levels

“…Thirty-two male and thirty-two female Swiss mice were housed in groups of four, with food and water ad libitum, in an experimental room, with controlled temperature (24 ± 2 • C) and light conditions (light/dark cycle of 12 h; lights on at 7:00 a.m.). Swiss mice were used owing to their sensitivity to the stimulant effects of ethanol, making them useful for studying behavioral sensitization in male and female mice [30,31].…”

Marc Richelle (1930–2021) and the Study of Temporal Regulation of Behaviour in Animals

“…If Richelle was, at least in part, an accidental psychopharmacologist, he was certainly an active one, producing more than twenty articles on the subject, and work on psychopharmacology and behavioural neuroscience continues to this day in the laboratory he founded (e.g., Didone, van Ingelgom, Tirelli, & Quartemont, 2019 ; Serrano et al, 2019 ). However, as well as pharmacological work, in his early years Richelle also conducted some purely behavioural studies, and I will mention two of the more unusual ones.…”