CAFFEINE AND THE OLFACTORY-BULB

Caffeine, a popular CNS stimulant, is the most widely used neuroactive drug. Present in coffee, tea, chocolate, and soft drinks as well as o ver-the-counter and prescription medications, it influences millions o f users. This agent has achieved recent notoriety because its dependen cy consequences and addictive potential have been re-examined and emph asized. Caffeine's central actions are thought to be mediated through adenosine (A) receptors and monoamine neurotransmitters. The present a rticle suggests that the olfactory bulb (OB) may be an important site in the brain that is responsible for caffeine's central actions in sev eral species. This conclusion is based on the extraordinarily robust a nd selective effects of caffeine on norepinephrine (NE), dopamine (DA) , and particularly serotonin (5HT) utilization in the OB of mice. We b elieve that these phenomena should be given appropriate consideration as a basis for caffeine's central actions, even in primates. Concurren tly, we review a rich rodent literature concerned with A, 5HT, NE, and DA receptors in the OB and related structures along with other monoam ine parameters. We also review a more limited literature concerned wit h the primate OB. Finally, we cite the literature that treats the depe ndency and addictive effects of caffeine in humans, and relate the fin dings to possible olfactory mechanisms.