Role Of Hippocampus In Regulating Slow Wave Sleep

The role and mechanism of hippocampus on sleep were investigated with the methods of polysomnography, sterotaxic surgery, microinjection and lesions of nuclei . Results as follows:1. The effects of L-glutamate and Y -aminobutyric acid in the hippocampus on sleep-wakefulnessMicroinjection of L-glutamate ( L-Glu , 1.0ug) into the hippocampus decreased wakefulness ( W ) and increased both slow wave sleep ( SWS ) and SWSa . However , microinjection of Y -aminobutyric acid ( GABA , 1.0 u g ) into the hippocampus decreased SWS and increased W .2. The effects of acetylcholine in the hippocampus on sleep-wakefulness Microinjection of acetylcholine ( ACh , 1.0 ug ) into the hippocampus enhancedW and decreased both SWS and SWSa . Microinjection of atropine ( 1.0 ug ) , a muscarinic receptor blocker , promoted SWS and abolished the effect of ACh .3. The effects of monoaminal neurotransmitter in the hippocampus on sleep-wakefulness3.1 noradrenalineMicroinjection of noradrenaline ( NA , l.Oug ) into the hippocampus enhanced SWS and reduced W ; Propranolol ( 1.0 ug ) , a 3 -adrenoceptor blocker , not only decreased SWS , but also abolished the SWS-promoting effect of NA ; Phentolamine (1.0 ug ),a a -adrenoceptor blocker , had no direct effect on sleep , and couldn't block the effect of NA either .3.2 5 -hy droxytryptamineMicroinjection of 5-hydroxytryptaphan ( 5-HTP , 1.0 ug ), the immediate precursorof 5-HT , into the hippocampus , enhanced SWS and SWS2 , but decreased W . Microinjection of methlysergide ( MS , 1.0 ug ), an antagonist of 5-HT receptor , into the hippocampus , had no direct effect on sleep , but abolished the SWS-promoting effect of 5-HTP completely .4. The effects of nitric oxide in the hippocampus on sleep-wakefulness Microinjection of nitric oxide synthase ( NOS ) inhibitor , N-nitro-L-arginine( L-NNA , 2.0 ug ) into the hippocampus reduced W , but increased both SWS and SWS2 . Microinjection of sodium nitroprusside ( SNP , 0.2 u g), a NO donor , into the hippocampus , not only increased W , but also abolished the SWS-promoting effect of L-NNA . After microinjection of L-arginine ( L-Arg , 0.4 ug ) , a precursor of NO , into the hippocampus , no significant change of SWS and W were found , but L-Arg blocked the effect of L-NNA .5. The effects of microinjection of insulin , naloxone and cyclic adenosine monophosphate into the hippocampus on sleep-wakefulnessMicroinjection of insulin ( 0.12" ) into the hippocampus increased SWS and decreased W . Microinjection of naloxone ( 1.0 ug ) , the antagonist of the opiate receptors , into the hippocampus , enhanced SWS and reduced W . Microinjection of cyclic adenosine monophosphate ( cAMP , 1.0 ug) into the hippocampus decreased W and increased SWS .These results indicated that:1. Microinjection of L-Glu into the hippocampus promotes SWS and decreases W , however , microinjection of GABA into the hippocampus decreases SWS and enhances W . These results show that the hippocampus play an important role in regulating sleep and wakefulness .2. NA, 5-HT, insulin and cAMP in the hippocampus promote SWS , however, ACh , NO and opioid inhibit SWS . The SWS-promoting effect of NA is mediated by 3 -adrenoceptor, and the W-promoting effect of ACh is mediated by muscarinic receptor . 3. Atropine , 5-HTP , L-NNA and naloxone increase the deep slow wave sleep , these findings provide some objective and effective dues for us to discover the new drug which not only treat the insomnia, but also promote the deep slow wave sleep .