Ethanol, diazepam, and scopolamine alter murine learning function and memory; ethanol changes halothane minimum alveolar concentration.

Abstract

The minimum alveolar anesthetic concentration of halothane (MACh) was tested by the tail clamping method in 12 male white albino mice and found to be 1.1 %. A further 24 mice were given 15% alcohol to drink for 60 days, after which they were divided into four groups of six mice each. One group was tested for MACh immediately after withdrawal from alcohol and the remaining groups were tested 4, 10, and 18 days later. In the first group MACh was 0.6%. It rose to 1.1% 4 days later and gradually reached 1.6% after an additional 14 days. Before receiving alcohol the mice were starved for 24 hours and placed in a maze containing food. The time taken to reach the food was recorded. The mice completed their way through the maze in 147 ± 21 seconds on the first run and in 73 ± 10 seconds on a second run, after which they made no further significant progress. During the first 9 days on alcohol mice made their way through the maze in an average of 178 ± 17 seconds (no memory). On the 10th day they went through the maze in 160 ± 17 seconds on the first run (still no memory) but in 59 ± 8 seconds on a second run (regained learning function) (p < 0.0005). A control group of six mice trained in the maze continued to cover it at maximal speed after a rest period of 10 days. An additional seven mice were given diazepam, 0.33 μg/g of body weight and another six mice, scopolamine, 0.13 μg/g of body weight, both intraperitoneally. They had been previously trained in the maze. Both groups lost their memory and ability to learn their way through the maze but regained the latter in a week. Alcohol, diazepam, and scopolamine all induce retrograde amnesia and loss of learning function, but the latter returns after 8 to 10 days. It is difficult to correlate the loss of memory and the ability to learn caused by alcohol with the changes alcohol produces in MACh.