SLEEP EFFECTS FOLLOWING INTRATHECAL ADMINISTRATION THE 5-HT1A AGONIST 8-OH-DPAT AND THE NMDA ANTAGONIST AP-5 IN RATS

The modulating effect of an intrathecally (i.t.) administered 5-HT1A agonist and an NMDA antagonist on sleep, waking and EEG power spectra was investigated in rats. The 5-HT1A agonist 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT) (38 nmol) increased total slow wave sleep (TSWS) and decreased waking over the 8 h recording period. The TSWS increase was mostly due to an increase in SWS1. Sleep latency to SWS1 was also reduced. The NMDA antagonist dl-2-amino 5-phosphonovaleric acid (AP-5) (31.5 nmol) reduced waking. SWS1 was increased, but TSWS was not changed. An increase in REM sleep was seen during the last part of the recording. Combined treatment with 8-OH-DPAT and AP-5 reduced waking and increased TSWS. No change in REM sleep was seen. There were no systematic changes in either waking, TSWS or REM fronto-frontal or fronto-parietal EEG power spectrum after any of the treatments. The results suggest that in the spinal cord stimulation of 5-HT1A receptors have a dampening effect on transmission of sensory information, leading to deactivation and thereby increased possibilities for sleep induction. Blockade of the NMDA receptors may also lead to a small dampening of sensory transmission with similar consequences.