Changes in sleep patterns by intralaminar thalamic microinjection of fluoxetine in rats

Sleep patterns were investigated in rats by analysis of EEG recorded for 6 hours following fluoxetine or saline (control) microinjection into the centromedial intralaminar thalamus (CIT) at either 9:30 AM or 1:30 PM, 4 or 8 hours after lights on, respectively. The treatment of fluoxetine at 9:30 AM did not affect any sleep patterns. In contrast, fluoxetine significantly suppressed total paradoxical sleep (PS) time and the number of PS episodes during the second and third hour after administration at 1:30 PM. In addition, microinjection of fluoxetine produced an apparent enhancement of the duration of slow wave sleep (SWS) episodes and a small non-significant increase in total SWS time. On the other hand, no obvious changes in the basal sleep-wakefulness pattern were found between the two saline-treated control groups. These results indicate that CIT microinjection of fluoxetine at different time points acts differentially in sleep patterns and suggest that CIT may be one of the action sites for peripherally administered fluoxetine to alter sleep patterns.