Effects And Mechanism Of Nucleus Reticularis Thalami On Sleep-Wakefulness Cycle Of Rats

The effects and mechanism of GABAergic neurons, NOergic neurons, opioid peptide and cyclic adenosine monophosphate (cAMP) in the nucleus reticularis thalami (RT) on sleep-wakefulness cycle of rats and the effects and mechanism of the 5-HTergic nerve fibers project from the nucleus raphes dorsalis (DRN) to RT on sleep-wakefulness cycle of rats were investigated with the methods of brain stereotaxic, nucleus spile, microinjection and polysomngraphy (PSG).1. The effects of GABAergic neurons in RT on sleep-wakefulness cycle of rats1.1 Microinjection of 3-mercaptopropionic acid (3-MP, a kind of glutamate decarboxylase inhibitor) into RT. On the day of microinjection, sleep only decreased a litter. On the second day, sleep marked decreased and wakefulness marked increased. On the third and fourth day, sleep and wakefulness stages resumed to normal.1.2 Microinjection of gamma-amino butyric acid (GABA 1.0μg) into RT enhanced sleep and reduced wakefulness compared with control; while microinjection of L-glutamate (L-Glu, 0.2μg) decreased sleep and increased wakefulness; microinjection of bicuculline (BIC, 1.0μg), a GABAA receptor antagonist, enhanced wakefulness and reduced sleep; microinjection of baclofen (BAC, 1.0μg), GABAB receptor agonist, had the same effects as GABA.2. The effects of NOergic neurons in RT on sleep-wakefulness cycle of rats2.1 Microinjection of L-arginine (L-Arg, 0.5μg) into RT decreased sleep compared with control, but there were on statistaical difference between L-Arg group and control; while microinjection of sodium nitroprusside (SNP, 0.2μg), a NO donor into RT, sleep marked decreased and wakefulness marked increased. Microinjection of nitric oxide synthase (NOS) inhibitor, N-nitro-L-arginine (L-NNA, 2.0μg) into RT enhanced sleep and reduced wakefulness.2.2 After simultaneous microinjection of L-NNA (2.0μg) and SNP (0.2μg) into RT, SNP abolished the sleep-promoting effect of L-NNA compared with L-NNA group; after simultaneous microinjection of L-NNA (2.0μg) and L-Arg(0.5μg) into RT, we found that L-NNA could not blocked the wakefulness-promoting effect of L-Arg.3. The effects of opioid peptide in RT on sleep-wakefulness cycle of rats3.1 Microinjection of morphine sulfate (MOR, 1.0μg) into RT increased wakefulness and decreased sleep compared with control; while microinjection of naloxone hydrochloride (NAL, 1.0μg) , the antagonist of opiate receptors, into RT, enhanced sleep and reduced wakefulness.3.2 After simultaneous microinjection of MOR (1.0μg) and NAL (1.0μg) into RT, the wakefulness-promoting effect of MOR and the sleep-promoting effect of NAL were not observed compared with control.4. The effects of cAMP in RT on sleep-wakefulness cycle of rats Microinjection of cAMP (1.0μg) into RT increased sleep and decreased wakefulness compared with control; microinjection of methylene blue (MB,1.0μg) into RT enhanced sleep and reduced wakefulness compared with control.5. The effects of the 5-HTergic nerve fibers project from DRN to RT on sleep-wakefulness cycle of rats5.1 When L-Glu (0.2μg) was microinjected into DRN and normal sodium (NS,1.0μg) was microinjected into bilateral RT. We found that sleep was decreased and wakefulness was increased compared with control; when L-Glu (0.2μg) was microinjected into DRN and methysergide (MS,1.0μg), a non-selective 5-HT antagonist, was microinjected into bilateral RT, We found that sleep was enhanced and wakefulness was reduced compared with L-Glu group.5.2 When p-chlorophenylalanine (PCPA, 10μg) was microinjected into DRN and NS (1.0μg) was microinjected into bilateral RT, We found that sleep was increased and wakefulness was decreased compared with control; microinjection of 5-hydroxytryptaphan (5-HTP, 1.0μg), which can convert to 5-HT by the enzyme tryptophane hydroxylase and enhance 5-HT into bilateral RT, could block the effect of microinjection of PCPA into DRN on sleep-wakefulness cycle.The present study indicated:1. GABA receptor in RT takes part in sleep-wake cycle and this mechanism is mediated by GABAA,GABAB receptors.2. NO and MOR have wakefulness-promoting effect in the RT of rats and the wakefulness-promoting effect is mediated by cAMP and cGMP. pathway3. Neural pathway of serotonin in DRN-RT may take part in the regulation of sleep-wake cycle. Blocking serotonin receptors in RT could prevent the wakefulness-promoting effect due to the excitation of DRN, while enhancement of 5-HT in RT could reverse the sleep-promoting effect caused by the 5-HT diminution in DRN.