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***<***N>是<***N>在<***N>茄科<***N>植物<***N>构成<***N>的<***N>烟草<***N>干重<***N>约<***N>0.6-3.0<***N>％<***N>的<***N>家庭<***N>（<***N>茄科<***N>）<***N>中<***N>发现<***N>的一种***<***N>，<***N>发生<***N>在叶片<***N>根部<***N>和<***N>积累<***N>的<***N>生物合成<***N>。<***N>它<***N>作为一个<***N>特别<***N>特异性<***N>昆虫<***N>antiherbivore<***N>化学<***N>功能;<***N>因此，<***N>***<***N>被广泛作为<***N>杀虫剂<***N>的<***N>使用<***N>，目前<***N>，如<***N>吡虫啉<***N>***<***N>类似物<***N>继续<***N>被广泛使用<***N>。
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Nicotine is an alkaloid found in the nightshade family of plants (Solanaceae) that constitutes approximately 0.6–3.0% of the dry weight of tobacco, with biosynthesis taking place in the roots and accumulation occurring in the leaves. It functions as an antiherbivore chemical with particular specificity to insects; therefore nicotine was widely used as an insecticide in the past, and currently nicotine analogs such as imidacloprid continue to be widely used.
In low concentrations (an average cigarette yields about 1 mg of absorbed nicotine), the substance acts as a stimulant in mammals and is the main factor responsible for the dependence-forming properties of tobacco smoking. According to the American Heart Association, nicotine addiction has historically been one of the hardest addictions to break, while the pharmacological and behavioral characteristics that determine tobacco addiction are similar to those determining addiction to heroin and cocaine. Nicotine content in cigarettes has slowly increased over the years, and one study found that there was an average increase of 1.6% per year between the years of 1998 and 2005. This was found for all major market categories of cigarettes.
Research in 2011 has found that nicotine inhibits chromatin-modifying enzymes (class I and II histone deacetylases) which increases the ability of cocaine to cause an addiction.
In low concentrations (an average cigarette yields about 1 mg of absorbed nicotine), the substance acts as a stimulant in mammals and is the main factor responsible for the dependence-forming properties of tobacco smoking. According to the American Heart Association, nicotine addiction has historically been one of the hardest addictions to break, while the pharmacological and behavioral characteristics that determine tobacco addiction are similar to those determining addiction to heroin and cocaine. Nicotine content in cigarettes has slowly increased over the years, and one study found that there was an average increase of 1.6% per year between the years of 1998 and 2005. This was found for all major market categories of cigarettes.
Research in 2011 has found that nicotine inhibits chromatin-modifying enzymes (class I and II histone deacetylases) which increases the ability of cocaine to cause an addiction.