Why giving up smoking is a drag

Abstract

Although a substantial body of evidence indicates that nicotine is the key constituent within tobacco smoke that leads to addiction, rather less is known about the mechanism through which this effect is mediated. Withdrawal from chronic nicotine administration does induce an abstinence syndrome in rats in keeping with the effects of withdrawal from other drugs of abuse, such as ethanol, sedative-hypnotics and opiates. However, the somatic symptoms that characterize these abstinence syndromes in animals are not thought to be as important to the motivational aspects of drug dependence in humans as the affective and emotional changes that occur. Epping-Jordan et al.[1xDramatic decrease in brain-reward function during nicotine withdrawal. Epping-Jordan, M.P. et al. Nature. 1998; 393: 76–79Crossref | PubMed | Scopus (471)See all References[1]now report that the emotional effects of nicotine withdrawal are similar to those observed during withdrawal from other addictive drugs, as measured by elevated intracranial self-stimulation (ICSS) brain-reward thresholds. These are suggested to represent a decrease in brain-reward function. Nicotine was administered to rats for a period of seven days via subcutaneous osmotic pumps. The levels of nicotine in the blood plasma were equivalent to those observed in smokers consuming 30 cigarettes a day. ICCS reward thresholds and somatic withdrawal signs were then measured following removal of the osmotic pumps. The elevated ICCS reward thresholds were observed four hours after pump removal and persisted for four days. The authors draw parallels between the decreased brain-reward function observed during nicotine withdrawal and the negative affective states reported by smokers during the first days of abstinence. These data could provide a model for the study of the affective effects of nicotine withdrawal in humans.