Nicotine contradictory effects

In summary, although the results on adolescent exposure are somewhat contradictory, females are apparently more sensitive than males to the effects of nicotine on locomotor activity, and the ovarian hormones are likely to underhe this greater responsivity. 

Only a few physiological studies on the actions of acetylcholine in the cerebellar cortex have been reported and the results of these studies were often contradictory lonto-phoretic application of acetylcholine has been observed to mildly excite Purkinje cells via a muscarinic (Crawford et al., 1966) or a nicotic (McCance and Phillis, 1968) mechanism, or to inhibit them via a mixed muscarinic and nicotinic mechanism. For interneurons no effect of acetylcholine was found by Crawford et al. (1966), whereas De la Garza et al. (1987) found a strong nicotinic excitatory effect. Crepel and Dhanjal... 

The amount of the substance and mode of eiqiosure is much more important than any assumed tolerance that might develop toward poisons. A careful look at Table 1.3 will reveal a number of natural and artificial substances listed such as paracetamol, aspirin, caffeine, sodium nitrite and nicotine, which are more or less toxic, but still used in everyday life. This might seem contradictory at first sight, but there is a marked dose-response relationship. A lot of toxic substances may also have positive effects and can be used if there is a large difference between beneficial and toxic doses. There is an old Latin saying sola dosis facit venenum—it is the dose that makes the poison. Even very toxic botulinum toxin has an everyday use in cosmetics, it removes wrinkles when applied cautiously on the forehead between the eyebrows. This Botox cure has an effect for more than half a year a lot of celebrities use it instead of plastic surgeries. 

Several studies, in part contradictory, are available concerning the influence of nicotinic acid on cholesterol biosynthesis. Perry (1960) reported from work with rat liver slices a decreased incorporation of C-acetate into cholesterol with high concentrations of nicotinic acid in the medium Schade and Saltman (1959) had obtained similar results in rabbits fed with nicotinic acid. On the other hand, Merrill and Lemley-Stone (1957) found increased cholesterol synthesis in liver slices of rats fed nicotinic acid, while Duncan and Best (1960) reported that nicotinic acid has no effect on C-acetate incorporation. Parsons (1961 a) studied the effects of nicotinic acid and niacin on incorporation of C-acetate in man, and stated that considerably less conversion into serum cholesterol (free and esterifled) and into erythrocyte cholesterol occurred during nicotinic acid administration. The concept of inhibition of cholesterol synthesis is also held by Goldsmith (1962) the point of inhibition supposedly occurs before the formation of squalene, because sterol intermediates between squalene and cholesterol could not be detected in serum. 

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