Reporting in the current online edition of the International Journal of Neuropsychopharmacology, UCLA psychiatry professor Dr. Arthur L. Brody and colleagues found that low-nicotine cigarettes act similarly to regular cigarettes, occupying a significant percentage of the brain's nicotine receptors.
Light cigarettes have nicotine levels of 0.6 to 1 milligrams, while regular cigarettes contain between 1.2 and 1.4 milligrams.
The researchers also looked at de-nicotinized cigarettes, which contain only a trace amount of nicotine (0.05 milligrams) and are currently being tested as an adjunct to standard smoking-cessation treatments. They found that even that low a nicotine level is enough to occupy a sizeable percentage of receptors.
"The two take-home messages are that very little nicotine is needed to occupy a substantial portion of brain nicotine receptors," Brody said, "and cigarettes with less nicotine than regular cigarettes, such as 'light' cigarettes, still occupy most brain nicotine receptors. Thus, low-nicotine cigarettes function almost the same as regular cigarettes in terms of brain nicotine-receptor occupancy.
"It also showed us that de-nicotinized cigarettes still deliver a considerable amount of nicotine to the brain. Researchers, clinicians and smokers themselves should consider that fact when trying to quit."
In the brain, nicotine binds to specific molecules on nerve cells called nicotinic acetylcholine receptors, or nAChRs. When nerve cells communicate, nerve impulses jump chemically across gaps between cells called synapses by means of neurotransmitters. The neurotransmitters then bind to the receptor sites on nerve cells — in the case acetylcholine resulting in the release of a pleasure-inducing chemical called dopamine. Nicotine mimics acetylcholine, but it lasts longer, releasing more dopamine.
"It can cause specific neurons to communicate and thus increases dopamine for an extended period of time," Brody said. "Most scientists believe that's one key reason why nicotine is so addictive."
In an earlier study, researchers determined that smoking a regular, non-light cigarette resulted in the occupancy of 88 percent of these nicotine receptors. However, that study did not determine whether inhaling nicotine or any of the thousands of other chemical found in cigarette smoke resulted in this receptor occupancy. The central goal of the present study was to determine if factors associated with smoking — other than nicotine — resulted in nAChR occupancy.
The authors reasoned that if nicotine is solely responsible for receptor occupancy, then smoking a de-nicotinized cigarette or a low-nicotine cigarette would result in the occupancy of roughly 23 percent and 78 percent of nicotine receptors, respectively, based on the cigarettes' nicotine content.
"That would still be substantial," Brody said.
Fifteen smokers participated in the study. Each was given positron emission tomography (PET) scans, a brain-imaging technique that uses minute amounts of radiation-emitting substances to tag specific molecules. In this case, the tracer was designed to bind to the nicotine receptors in the brain.
The researchers could then measure what percentage of the tracer was displaced by nicotine when the research subjects smoked. In total, 24 PET scans were taken of participants' brains before and after three different conditions: not smoking, smoking a de-nicotinized cigarette and smoking a low-nicotine cigarette.
The PET data showed that smoking a de-nicotinized cigarette and a low-nicotine cigarette occupied 26 percent and 79 percent of the receptors, respectively, which was very close to what the researchers had originally estimated.
"Given the consistency of findings between our previous study with regular cigarettes and the present study — that showed us that inhaling nicotine during smoking is solely responsible for occupancy of brain nicotine receptors," Brody said.
In addition to Brody, other authors of the study were Mark A. Mandelkern, Matthew R. Costello, Anna L. Abrams, David Scheibal, Judah Farahi, Edythe D. London, Richard E. Olmstead, Jed E. Rose and Alexey G. Mukhin. The researchers report no conflicts of interest. Rose, from the Duke University School of Medicine, has received research support for a study unrelated to the present paper from Vector Tobacco Inc., the manufacturer of Quest cigarettes.
The research was supported by the National Institute on Drug Abuse, the Veterans Administration, the Tobacco-Related Disease Research Program, the National Alliance for Research on Schizophrenia and Depression, and the Office of National Drug Control Policy.
Mark Wheeler | EurekAlert!
New malaria analysis method reveals disease severity in minutes
14.08.2017 | University of British Columbia
New type of blood cells work as indicators of autoimmunity
14.08.2017 | Instituto de Medicina Molecular
Whether you call it effervescent, fizzy, or sparkling, carbonated water is making a comeback as a beverage. Aside from quenching thirst, researchers at the University of Illinois at Urbana-Champaign have discovered a new use for these "bubbly" concoctions that will have major impact on the manufacturer of the world's thinnest, flattest, and one most useful materials -- graphene.
As graphene's popularity grows as an advanced "wonder" material, the speed and quality at which it can be manufactured will be paramount. With that in mind,...
Physicists at the University of Bonn have managed to create optical hollows and more complex patterns into which the light of a Bose-Einstein condensate flows. The creation of such highly low-loss structures for light is a prerequisite for complex light circuits, such as for quantum information processing for a new generation of computers. The researchers are now presenting their results in the journal Nature Photonics.
Light particles (photons) occur as tiny, indivisible portions. Many thousands of these light portions can be merged to form a single super-photon if they are...
For the first time, scientists have shown that circular RNA is linked to brain function. When a RNA molecule called Cdr1as was deleted from the genome of mice, the animals had problems filtering out unnecessary information – like patients suffering from neuropsychiatric disorders.
While hundreds of circular RNAs (circRNAs) are abundant in mammalian brains, one big question has remained unanswered: What are they actually good for? In the...
An experimental small satellite has successfully collected and delivered data on a key measurement for predicting changes in Earth's climate.
The Radiometer Assessment using Vertically Aligned Nanotubes (RAVAN) CubeSat was launched into low-Earth orbit on Nov. 11, 2016, in order to test new...
A study led by scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg presents evidence of the coexistence of superconductivity and “charge-density-waves” in compounds of the poorly-studied family of bismuthates. This observation opens up new perspectives for a deeper understanding of the phenomenon of high-temperature superconductivity, a topic which is at the core of condensed matter research since more than 30 years. The paper by Nicoletti et al has been published in the PNAS.
Since the beginning of the 20th century, superconductivity had been observed in some metals at temperatures only a few degrees above the absolute zero (minus...
16.08.2017 | Event News
04.08.2017 | Event News
26.07.2017 | Event News
17.08.2017 | Physics and Astronomy
17.08.2017 | Earth Sciences
17.08.2017 | Physics and Astronomy