Effects of ageing and intermittent ethanol exposure on rat locus coeruleus and ethanol-withdrawal symptoms

In this study, the effects of ethanol and age on the morphology of the locus coeruleus (LC) and on the severity of ethanol-withdrawal symptoms were studied during a 5-week intermittent ethanol exposure. Young (3-4 months) and old (29-30 months) male Wistar rats were given highly intoxicating doses of ethanol by intragastric intubations for 4 days, followed by a 3-day ethanol-withdrawal period. This 7-day cycle of ethanol exposure and withdrawal was repeated five times. A non-treated group and a sucrose-fed group of both ages were used as control groups. The severity of ethanol-withdrawal symptoms (rigidity, tremor, irritability, hypoactivity) was rated up to 62 h after the last dose of ethanol. The intoxication level was higher in the old, compared with the young, rats, despite the smaller doses of ethanol given to the old animals. There was no significant difference between the age groups in the severity of the ethanol-withdrawal syndrome. The LC quantitative studies were performed using unbiased stereological methods. The results showed that there was no difference between the age groups in the LC total neuron numbers of the non-treated control groups. The 5-week intermittent ethanol exposure significantly reduced the LC neuron numbers and LC neuronal density in the old ethanol-exposed animals, compared with the sucrose-fed control animals. In the young rats, the ethanol-induced neuron loss did not reach statistical significance. According to the ANCOVA, the difference in the ethanol-induced LC neuronal loss between the age groups may be due to the difference in the intoxication levels. Interestingly, the sucrose intubations were also found to decrease the LC neuronal numbers in the young rats, compared with the non-treated young control group. It was concluded that ageing did not significantly affect the severity of ethanol-withdrawal symptoms or ethanol-induced loss of LC neurons in Wistar rats.