| Objection: Sleep-wake cycle is a kind of biological rhythm. The nucleus of solitarius tractus (NST) is an important site for the intergration of visceral information and its modification by afferent neural systems. As for a sleep-inducing area of lower brain stem, it is related with sleep disturbance of visceral diseases, but these mechanisms are unclear. 5-hydroxytryptamine (serotonin, 5-HT) is an important kind of monoaminergic neurotransmitters. In the present study, a method of stereotaxic apparatus was employed to fix a guide cannula in the NST which was used as a way to microinject 5-HT 's related drugs. Then we can analyze electroencephalogram (EEG) to specify the signal transduction pathways through which 5-HT generate sleep in the NST. In addition, we furthered to understand that NST plays a role in the paradoxical sleep (PS), providing a foundation of emulating mechanism of sleep and treating some sleep disturbance involved visceral diseases and a new target point about developing a new medicine.Methods: 1. Subjects: Male Sprague Dawley rats (220-260 mg) were purchased from military medical institution at Beijing.2. Animal surgery: SD rats were operated under the acetylglycinamide-chloral diphosphate (AGAC) anesthesia for the implantation of chronically dwelling electrodes for recording the EEG and electromyogram (EMG) and received a fixed guide cannula in the NST, according to the atlas of Paxinos and Watson. Animals were allowed to refresh 5 days after surgery in the animal room before being placed in recording chambers for the duration of the experiment.3. Recording EEG and EMG: The EEG and EMG signals were collected using a NIHON KOHOEN (No7213) polygragh and subsequently analyzed according to the standard regulation. Animals were recorded 4 hours every day and continuallylasted 4 days.4.Perfusion and fixation: after recording, the animals were killed under AGAC anesthesia by intra-aortic perfusion of a fixative solution (containing 4%paraformaldehyde) and their brains were taken out using paraffin buried and HE staining; another 3 groups animals samples were used to a freezing microtome and immunohistochemical staining.5. Statistical analysis: All the data were done by methods of pair t-test with SPSS10.0 statistical procedure. Significance level was chosen at 0.05 and all tests were two-sided.Results: 1. Using pair t-test, normal saline (NS) group is not significantly different as a control group; 5-hydroxytryptophan (5-HTP) group, 8-OH-DPAT, H89 are significantly different on the decline of wake, increase of SWS and PS ; methysergide (MS) group is not significantly different ; spiperone group and cAMP group are significantly different on the increase of wake and the decline of SWS and PS.2. 5-HT1A receptor (5-HT1AR) of immunohischemical data in the NST between NS group, 5-HTP group and MS group: Compared with NS group, there is uptake of 5-HT1AR in 5-HTP group and downtake of 5-HT]AR in MS group.3. 5-HTnergic neural fibers of immunohischemical data in the NST between NS group, 5-HTP group and MS group: Compared with NS group, there is strong stain of 5-HTnergic neural terminal fibers in 5-HTP group and light stain of 5-HTnergic neural terminal fibers in MS group.4. 5-HTiAR of immunohischemical data in the midbrain of NS group: there are widely distribution of 5-HT1AR immunoreactivity in the midbrain, especially in the raphe nuclei (RN), LDT/PPT of reticular formation.5. 5-HTnergic neural terminal fibers of immunohischemical data in the midbrain between NS group, 5-HTP group and MS group: compared with NS group, thereare few numbers of 5-HT neuron in 5-HTP group and more in MS group. Conclusions: 1. As an inducing area, 5-HT in the NST plays an important role in the sleep-wake cycle.2. Sleep generation is mediated by 5-HT1AR-activated signal transduction pathway involving aGi/G0-like G-protein in 5-HT microinjecting NST on sleep-wake cycle, which is caused to decline wake time and increase sleep time.3. There is increase in SWS following the incre...
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