Ventral striatal dopamine release in response to smoking a regular vs a denicotinized cigarette

Abstract

Prior studies have demonstrated that both nicotine administration and cigarette smoking lead to dopamine (DA) release in the ventral striatum/nucleus accumbens. In tobacco-dependent individuals, smoking denicotinized cigarettes leads to reduced craving, but less pleasure, than smoking regular cigarettes. Using denicotinized cigarettes and (11)C-raclopride positron emission tomography (PET) scanning, we sought to determine if nicotine is necessary for smoking-induced DA release. Sixty-two tobacco-dependent smokers underwent (11)C-raclopride PET scanning, during which they smoked either a regular or denicotinized cigarette (double-blind). Change in (11)C-raclopride binding potential (BP) in the ventral striatum from before to after smoking was determined as an indirect measure of DA release. Cigarette craving, anxiety, and mood were monitored during scanning. Smoking a regular cigarette resulted in a significantly greater mean reduction in ventral striatal (11)C-raclopride BP than smoking a denicotinized cigarette. Although both groups had reductions in craving and anxiety with smoking, the regular cigarette group had a greater improvement in mood. For the total group, change in BP correlated inversely with change in mood, indicating that greater smoking-induced DA release was associated with more smoking-related mood improvement. Thus, nicotine delivered through cigarette smoking appears to be important for ventral striatal DA release. Study findings also suggest that mood improvement from smoking is specifically related to ventral striatal DA release.

Figure 1

Scatterplot showing percent change in ¹¹C-raclopride binding potential (BP) for the group that smoked a denicotinized cigarette (−1.2 ( ± 2.5)%; n = 16) and the group that smoked a regular cigarette (−8.4 ( ± 1.5)%; n = 46). The group that smoked a denicotinized cigarette had less of a decrease in ¹¹C-raclopride BP than the group that smoked a regular cigarette, indicating that nicotine inhalation is important for dopamine release.

Figure 2

Scatterplot showing the negative correlation (r = −0.33, p = 0.01) between percent change in ¹¹C-raclopride binding potential (BP) (an indirect measure of dopamine release) and percent change in mood analog rating scale score for the total group of tobacco-dependent smokers (n = 62).