Elevated Plus Maze. Apparatus The Elevated Plus Maze (EPM) was made of grey PVC and consisted of four arms, forming a ‘plus’ shape, elevated by four extendible metal rods, 100 cm above ground level. The rods were supporting the ends of the four arms. The arms were 28 xx xxxx and 6 cm in width. Two opposite arms were surrounded by transparent Plexiglas walls of 15 cm in height (the ‘closed’ arms); the other two opposite arms did not have surrounding walls (the ‘open’ arms). The center, where the four arms connect, consisted of a square area measuring 6x6 cm. Behavioral parameters were analyzed by digitizing film material using a computer program. To this end, a camera hanging above the maze filmed the EPM during the entire experiment. Spatial cues were present in the testing room (i.e. posters on the walls). Light intensity was set at 80 Lux and 20 dB background noise was present in the testing room. The setup was cleaned with water after each mouse as described previously (Brinks, van der Mark et al. 2007).
Elevated Plus Maze. Behavioral Analyses
Elevated Plus Maze. Mice were handled once per day for two days prior to testing. Subjects were placed in the elevated plus maze apparatus to explore for 5 minutes in dim lighting. Behavior was hand- scored for time on open arms, time on closed arms, time in center, and number of entries into the open and closed arms.
Elevated Plus Maze. Subjects were handled once per day for the two days prior to testing. Subjects were placed in the elevated plus maze apparatus to explore for 5 minutes in dim lighting. Behavior was hand- scored for time on open arms, time on closed arms, time in center, and number of entries into the open and closed arms.
Elevated Plus Maze. We use the Elevated Plus Maze (EPM) as a way to look at exploratory and anxiolytic behavior in the mice. Occasionally, we have mice that move very little, or not at all, which shows the freezing response that rodents have when they are stressed. These mice normally get excluded with the outliers, because, typically, it will be a large duration of the time, sometimes the entire time, spent in one zone. Because of the dynamics of how the various zones of the EPM correlate to various environmental situations that would be encountered in the wild, we can assess the relative willingness that the animal has to explore or how much the animal wants to avoid a more dangerous environment. Behaviors can change throughout the estrous cycle, especially due to the rapid changes in the ratio of progesterone to estrogen that occur during proestrus and estrus (Maeng & Milad, 2015). We were curious about the impact that higher relative levels of circulating progesterone and its metabolites have on anxiety-related behavior in the context of the rapid tolerance to the anxiolytic effects of alcohol. We hypothesized that higher levels of circulating progesterone and its metabolites as seen in diestrus would result in a development of rapid tolerance to the anxiolytic effects of alcohol, due to the system being already prepped for relatively higher levels of these metabolites. In estrus females, the neural systems are not adjusted to relatively higher progesterone levels, meaning the development would not occur as quickly. In males, we expected to see a development of rapid tolerance in the anxiolytic effects of alcohol, similar to that seen in the experiment carried out in rats by Xxxxxxxxx in 2012. The initial experiment which looked at the effects of one 1g/kg dose of either saline or ethanol on behavior in the elevated plus maze, showed surprising results in the decrease of time spent in the open arms by the male mice who were exposed to ethanol as compared to those exposed to saline (Fig. 1a). This contradicts previous information and understandings about behavior, but this could also simply be an anomaly due to a very low sample size and individual variability. The females a slight increase in anxiolytic behavior with administration of ethanol compared to saline, which is the results that were anticipated by both sexes, based on previous findings. The data that was divided between sexes, with no regard for hormone status, showed us the first instance of rapid sensitization...
