Well, today makes it a month since I quit smoking cold turkey (yum, cold turkey). I had smoked for 20 years, quit for 10 years, then started again a week before we left for the UK in 2011. We were going to see friend who was dying of cancer and for whatever reason I had to have my cancer sticks. I am currently using something new to take the edge off. I believe it is called Heroin. But seriously, I have heard that Nicotine is more addictive than Heroin although the receptor pathway seems different.
Nicotine is a potent stimulant and parasympathomimetic alkaloid found in the nightshade family of plants. Nicotine acts as an exogenous receptor agonist at most nicotinic acetylcholine receptors (nAChRs), except at two nicotinic receptor subunits(nAChRα9 and nAChRα10) where it acts as a receptor antagonist.
Nicotine constitutes approximately 0.6–3.0% of the dry weight of tobacco. Usually consistent concentrations of nicotine varying from 2–7 µg/kg (20–70 millionths of a percent wet weight) are found in the edible family Solanaceae, such as potatoes, tomatoes, and eggplant. Some research indicates that the contribution of nicotine obtained from food is substantial in comparison to inhalation of second-hand smoke. Others consider nicotine obtained from food to be trivial unless exceedingly high amounts of certain vegetables are eaten. It functions as an antiherbivore chemical; consequently, nicotine was widely used as an insecticide in the past, and neonicotinoids, such as imidacloprid, are widely used.
Nicotine is highly addictive. It is one of the most commonly abused drugs. An average cigarette yields about 2 mg of absorbed nicotine, while high amounts can be harmful. Nicotine induces both behavioral stimulation and anxiety in animals.Nicotine addiction involves drug-reinforced behavior, compulsive use, and relapse following abstinence. Nicotine dependenceinvolves tolerance, sensitization, physical dependence, and psychological dependence. Nicotine dependency causes distress. Nicotine withdrawal symptoms include depressed mood, stress, anxiety, irritability, difficulty concentrating, and sleep disturbances. Mild nicotine withdrawal symptoms are measurable in unrestricted smokers, who experience normal moods only as their blood nicotine levels peak, with each cigarette. On quitting, withdrawal symptoms worsen sharply, then gradually improve to a normal state.
When taken orally, Heroin undergoes extensive first-pass metabolism via deacetylation, making it a prodrug for the systemic delivery of morphine. When the drug is injected, however, it avoids this first-pass effect, very rapidly crossing the blood–brain barrier because of the presence of the acetyl groups, which render it much more fat soluble than morphine itself. Once in the brain, it then is deacetylated variously into the inactive 3-monoacetylmorphine and the active 6-monoacetylmorphine (6-MAM), and then to morphine, which bind to μ-opioid receptors, resulting in the drug's euphoric, analgesic (pain relief), and anxiolytic (anti-anxiety) effects; heroin itself exhibits relatively low affinity for the μ receptor. Analgesia follows from the activation its G-protein coupled receptor, which indirectly hyperpolarize of the neurone, reduce the release of nociceptive neurotransmitters, and hence cause analgesia and increased pain tolerance.
Unlike hydromorphone and oxymorphone, however, administered intravenously, heroin creates a larger histamine release, similar to morphine, resulting in the feeling of a greater subjective "body high" to some, but also instances of pruritus (itching) when they first start using.
Normally GABA, released from inhibitory neurones, inhibits the release of dopamine. Opiates, like heroin and morphine, decrease the inhibitory activity of such neurones. This causes increased release of dopamine in the brain which is the reason for euphoric and rewarding effects of heroin.
Both morphine and 6-MAM are μ-opioid agonists that bind to receptors present throughout the brain, spinal cord, and gut of all mammals. The μ-opioid receptor also binds endogenous opioid peptides such as β-endorphin, Leu-enkephalin, and Met-enkephalin. Repeated use of heroin results in a number of physiological changes, including an increase in the production of μ-opioid receptors (upregulation). These physiological alterations lead to tolerance and dependence, so that stopping heroin use results in uncomfortable symptoms including pain, anxiety, muscle spasms, and insomnia called the opioid withdrawal syndrome. Depending on usage it has an onset 4–24 hours after the last dose of heroin. Morphine also binds to δ- and κ-opioid receptors.
Edited by fahrquad, 18 February 2019 - 08:37 PM.