If this it true it explain why napping after a session is always a great idea.
"Research suggests that, when smokers wish to achieve a stimulating effect, they take short quick puffs, which produce a low level of blood nicotine.
This stimulates nerve transmission
. When they wish to relax, they take deep puffs, which produce a high level of blood nicotine, which depresses the passage of nerve impulses
, producing a mild sedative effect. At low doses, nicotine potently enhances the actions of norepinephrine
in the brain, causing a drug effect typical of those of psychostimulants
. At higher doses, nicotine enhances the effect of serotonin
activity, producing a calming, pain-killing
effect. Nicotine is unique in comparison to most drugs
, as its profile changes from stimulant
in increasing dosages