Kilogram is used in the International System to measure mass, which is the amount of matter that an object contains. The kilogram was first based up on an object located in france which was a kilogram, and from that every scale and balances were calibrated, the problem was that it was decaying like every element on earth with time, that was created in 1889, and ever since it has been loosing weight because of this decay, it has los 50 micrograms, which is equivalent to a 2 cm hair or an eyelash, now is changing to be correlated to the planck constant, which never changes her or in the universe, this is very important because the SI is meant to be universal, for all the people throughout the time.
Nicotine, once in the brain, will work specifically on nicotinic receptors in the brain. However, there is a common "addiction" pathway in the brain that pretty much all addictive substances go through.
