Monoamine oxidase inhibition dramatically increases the motivation to self-administer nicotine in rats.

Nicotine is the major neuroactive compound of tobacco, which has, by itself, weak
reinforcing properties. It is known that levels of the enzymes monoamine oxidase
A (MAO-A) and MAO-B are reduced in the platelets and brains of smokers and that
substances, other than nicotine, present in tobacco smoke have MAO-inhibitory
activities. Here, we report that inhibition of MAO dramatically and specifically
increases the motivation to self-administer nicotine in rats. These effects were
more prominent in rats selected for high responsiveness to novelty than in rats
with low responsiveness to novelty. The results suggest that the inhibition of
MAO activity by compounds present in tobacco smoke may combine with nicotine to
produce the intense reinforcing properties of cigarette smoking that lead to
addiction.

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