M1 and M3 muscarinic receptors: specific roles in sleep regulation

P-fluoro-hexahydro-sila-difenidol hydrochloride (p-F-HHSiD) (15, 30 micrograms) and pirenzepine (7.5, 15, 30 micrograms), which are highly selective M3 and M1 muscarinic antagonists, respectively, were injected intracerebroventricularly into freely moving rats. p-F-HHSiD (30 micrograms) reduced wakefulness (W) (from 34.7 +/- 3.1 to 24.9 +/- 1.3 min) and increased slow wave sleep (SWS) (from 56.7 +/- 2.4 to 67.2 +/- 1.5 min); however, it did not modify desynchronized sleep (DS) latency and percentage in 6 h recordings. W and SWS were not affected by pirenzepine (7.5, 15, 30 micrograms) which decreased significantly DS amount but left unaffected DS latency. The results suggest that each muscarinic receptor subtype may induce different and specific changes in sleep phases and cortical desynchronization processes.