From New Orleans, La., at Experimental Biology 2002
Depressed individuals are far more likely than others in the population to take up smoking–and less successful in giving up a cigarette addiction. Researchers have long suspected that depressed people “may in fact be using cigarettes as a means to self-medicate with nicotine,” notes Khandra Tyler of the Howard University College of Medicine in Washington, D.C. She’s now found evidence to support nicotine’s therapeutic effect in rats that show symptoms resembling those of human depression.
When placed in a pool of water, normal rats usually swim vigorously until they can get out. Rats of the Wistar-Kyoto strain that Tyler studied instead remain rather immobile, floating instead of swimming, about half of the time. To test nicotine’s effects, she injected these rats twice daily for 9 days with a dose that roughly corresponds to the nicotine that a pack-a-day smoker might inhale. During 5 minutes in the pool, the treated animals swam about twice as much as their untreated brethren. However, nicotine didn’t increase the animals’ activity on dry land nor the pool activity of related rats that don’t model depression. This suggests, Tyler says, that drug makers might consider aiming new antidepressants at the brain’s nicotine receptors.