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Kenny PJ, Markou A. 
“Nicotine self-administration acutely activates brain reward systems and induces a long-lasting increase in reward sensitivity”. 
Neuropsychopharmacology. 2006 Jun;31(6):1203-11.
Abstract
Nicotine is a major component of tobacco smoke contributing to the initiation and persistence of the harmful tobacco habit in human smokers. The reinforcing effects of nicotine likely arise through its ability to stimulate brain circuitry mediating the detection and experiencing of natural rewards. Nevertheless, remarkably little is known concerning the acute or long-lasting actions of nicotine on brain reward systems in vivo. Here, we investigated the effects of intravenously self-administered nicotine (0.03 mg/kg/infusion, free base) on the sensitivity of brain reward systems, reflected in alterations of intracranial self-stimulation (ICSS) thresholds in rats. Rats self-administered nicotine during 1 or 12 h daily sessions, with reward thresholds assessed 1 h before and 15 min after each self-administration session. Control rats remained nicotine naïve throughout. Nicotine self-administration increased the sensitivity of brain reward systems, detected by post-nicotine lowering of reward thresholds in 1 and 12 h rats. This nicotine-enhanced sensitivity of reward systems was reversed by the high-affinity nicotinic receptor antagonist dihydro-beta-erythroidine (DHbetaE; 3 mg/kg). Surprisingly, nicotine-induced excitation of reward systems persisted for at least 36 days after nicotine self-administration had ceased. Overall, these data demonstrate that rats can voluntarily consume quantities of nicotine sufficient to increase the sensitivity of brain reward systems, an action likely crucial in establishing and maintaining the nicotine habit. Moreover, self-administered nicotine resets the sensitivity of reward systems to a new increased level, thereby imprinting an indelible 'memory' of its effects in reward systems, an action that so far appears unique to nicotine among drugs of abuse.Neuropsychopharmacology (2006) 31, 1203-1211. doi:10.1038/sj.npp.1300905; published online 28 September 2005.
Comments and Responses to this Article
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earth
Apr 17, 2011 1:59
Gateway Drug? #

This research may shed some light on how and why nicotine is such a powerfully addictive drug. It may cause everything else to seem more pleasurable and satisfying when it is in the body.

'Overall, these data demonstrate that rats can voluntarily consume quantities of nicotine sufficient to increase the sensitivity of brain reward systems, an action likely crucial in establishing and maintaining the nicotine habit.

Moreover, self-administered nicotine resets the sensitivity of reward systems to a new increased level, thereby imprinting an indelible 'memory' of its effects in reward systems, an action that so far appears unique to nicotine among drugs of abuse.' [Kenny 2006]


Smoke a cigarette and eat an apple, the apple seems to taste just a little bit more satisfying. If the same apple is eaten later, it is not quite as satisfying.

That sounds like it has some very interesting implications for future research.
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