Inhibition of REM sleep by fluoxetine, a specific inhibitor of serotonin uptake

Abstract

Fluoxetine, a specific inhibitor of serotonin uptake, suppressed REM sleep in cats. The onset of action was prompt and with doses of 2.5 mg/kg, (p.o.) the effect lasted a full 24 hr. After 2 or 3 weeks of daily dosing, the amount of REM sleep began to increase again. A small dose of fluoxetine added to a small dose of l-5-hydroxy-tryptophan caused a significant decrease in REM sleep whereas either treatment alone did not. Administered to cerveau isolé cats fluoxetine did not antagonize EEG desynchronization induced by the muscarinic stimulant arecoline, indicating the lack of a direct anticholinergic effect. These experiments indicate that REM sleep is suppressed when 5-HT accumulates at synapses as a consequence of fluoxetine administration. These data and a similar suppression of REM sleep that occurs when norepinephrine accumulates suggest that both NE and 5-HT can inhibit the cholinergic system that seems crucial for REM sleep. Non-REM sleep was usually increased in cats. In rats REM sleep was suppressed by fluoxetine but SWS did not increase.