Preserved Number of Orexin Neurons in Postmortem Hypothalamic Tissue of Chronic Alcoholics

Abstract

The hypothalamic orexin system is critically involved in addiction, including chronic alcohol abuse. Microinjection of orexin into the lateral hypothalamus increases alcohol intake in rats, while reduced immunoreactivity of orexin neurons is associated with decreased alcohol drinking. Recently, the numbers of orexin neurons were found to be increased in opiate addiction in humans [4] and cocaine addiction in rats [2], but the integrity of orexin neurons has not yet been studied in human alcoholics. We examined the hypothalamus of 9 patients of chronic alcoholism and 10 subjects without a history of alcoholism or any other neurological or psychiatric disorder. We performed immunohistochemistry for orexin A, followed by stereological quantification. The hypothalamic tissue of chronic alcoholics exhibited a slightly increased number (9%) of orexin-containing neurons compared to the control group (123’087 ± 18’536 and 110’431 ± 14’439, p = 0.11). Mean Gundersen’s coefficient of error was 0.06 ± 0.01. The number of orexin neurons was similar in chronic alcoholics and control subjects without a history of alcoholism. Further examination of alcohol-induced hypothalamic damage is needed to understand, whether a neuroplastic increase in orexin neurons counterbalances a concurrent alcohol-toxic damage to these neurons.