| Sleep is a very important life situation about one-third of our life time. In recent years, with the accelerated pace of life, sleep deprivation at night operation, and a variety of occupational groups are common, and sleep-related diseases such as insomnia, sleep disorders, the incidence of depression has increased year by year, so the current study has been more and more focus on the sleep mechanism in medical profession, biology and society.Many central nucleus regulated sleep-wake cycle, such as lateral preoptic area, suprachiasmatic nucleus, raphe nuclei, pineal gland and other parts, and they involved in the sleep center to maintain homeostasis of sleep. Habenular nucleus sites in the epithalamus and have fibers linked with these sleep center. In recent years, the function of the lateral habenular nucleus caused a number of the attention of scholars, especially in the effects of LHb in the pathogenesis of depression. And the most typical clinical manifestation of depression is a sleep disorder. Therefore, the lateral habenular nucleus may be involved in the regulation of sleep-wakefulness cycle. Lateral habenular received projection fibers from the retinal ganglion directly, which showed its own circadian rhythm activities. Furthermore the lateral habenular nucleus contains neurotransmitter, neuromodulator and its receptor, which is involved in regulation of sleep homestatstic. Lateral habenular nucleus received efferent from lateral preoptic area fiber which is a sleep-promoting center. Therefore, we speculated that the lateral habenular play an important role in the impact of sleep through the lateral preoptic area - lateral habenular nucleus way.To solve the above problem, first of all, we used EEG recording technique to study whether lateral habenular nucleus regulating sleep and affecting which parts of sleep as well as sleep deprivation.Then we used electrophysiological methods to explore the function between the lateral habenular nucleus and lateral preoptic area.Further immunohistochemical method was used to determine the lateral preoptic area - the lateral habenular nucleus pathway in the role of sleep-wake cycle.The research results showed that:(1) The effects of LHb regulating sleep-wake cycle:Following lesion of the LHb and compared with the rats before lesion, Wake time was increased (P<0.001). Meanwhile, NREMS was decreased (P<0.001). REM was decreased from (P>0.05), but showed no significantly difference. In lesion rat, wakefulness was increased from 213.02±8.5min to269.31±23.07min (t=-3.20 , P<0.05)and NREMS was decreased from 458.56±9.04min to 396.86±22.03min (t=4.262,P<0.01)during the light-on period. Whereas REM showed no significantly difference. In lesion rat, wakefulness was increased from 451.28±24.92 min to 519.67±13.81min (t=-2.583, P<0.05) during the light-off period. NREMS and REMS tended to decrease but this trend was not statistically significant.(2)The effects of LHb in the phonic reaction:In at 24 hours light continuous illumination, the wakfulness was reduced (P <0.05) and NREMS was increased (P <0.05), REMS was lower in normal rats (P> 0.05)compared with in the LD condition normal rats. But the lesion lateral habenular nucleus of rats showed no difference between in LD condition and DD condition (P> 0.05). The wake time and NREMS both the normal rats and lesion lateral habenular nucleus rats showed no significantly change both in LD and DD.(3) The effects of LHb in sleep deprivation:After the 6 hours of sleep deprivation, the wakefulness in lateral habenular rats was significantly greater than the normal rat group And detla activity in lesion rats was increased compared with normal rats during sleep deprivation time.It indicate that lateral habenular join in the depth of sleep (P <0.05). The theta activity of lesion rats was significantly lower than normal group (P <0.05) indicated the lateral habenular nucleus increased sleep tendency.(4) The effects of microinjection of AD antagonist into LHb in regulating sleep: After microinjection of adenosine receptor antagonist into lateral habenular nucleus, NREMS was significantly reduced from 148.28±3.51min to 137.31± 5.33min (t = 3.267, P<0.05). wakefulness was increased from 65.29±4.77min to 76.19±5.3min (t =- 2.608, P<0.05). REMS showed no change from 25.83±3.73min to 26.17±1.66min.(5) The electophysiological function between LHb and LPO:Application of single-pulse stimulation and tetanic methods to stimulate the lateral preoptic area and record the lateral habenular nucleus discharge showed that the discharge in lateral habenular nucleus was increased. Return stimulate lateral habenular nucleus and record the discharge of lateral preoptic area neurons show that the firing rate of LPO was reduced. After electic-lesion of stria medullary then uesd single pulse stimulation lateral preoptic area to record lateral habenular neurons showes no change.(6) The effects of GABA and Glu on the function between LHb and LPO:Electrochemical studies have shown that the effect of microinjection Glu into LPO on the firing rate of neurons in LHb was excited. The firing rate of LPO was decreased after microinjection of Glu in LHb. The effect of microinjection GABA into LPO on the firing rate of neurons in LHb was inhibition. The firing rate of LPO was increased after microinjection of GABA in LHb.(7) The effects of microinjection of AD and AD antagonist into LPO in the firing rates of LHb:The firing rate of LHb was increased after microinjection of AD into LPO (from 4.67±0.71Hz to 6.22±0.86Hz, P<0.05). The firing rate of LHb was increased after microinjection of 8-PT into LHb was significantly increased from 3.63±0.57Hz to 6.11±1.08Hz (P<0.05).(8) CTb and c-fos double staining:Immunohistochemical staining showed that Fos + CTb + cell count was increased in three hours of sleep deprivation 114.1±2.49, compared to in rats normal sleep group 16.25±1.01 (P <0.001)From the above results we can draw the following conclusions:(1) Application of animal EEG recording showed, wakefulness was increased and NREMS was decreased in lesion rat during the 24 hours compared with normal rats. It suggest that lateral habenular nucleus may play a critical role in the regulation of total amount of sleep. In LL, the wakfulness was reduced and NREMS was increased in normal rats,but the lesion lateral habenular nucleus of rats showed no difference between in LD condition and DD condition. Both the normal rats and lesion lateral habenular nucleus rats showed no significantly change both in LD and DD. These suggest that external light may be a key role in LHb regulating sleep.Microinjection of adenosine antagonists into LHb can increase the wake time, show that the lateral habenular approved as the role of endogenous adenosine targets involved in the regulation of sleep homeostasis.2. We used electrical stimulation, Glu and GABA, respectively, which chemical excited and inhibition LHb, sleep-promoting substance adenosine excited LPO.The effects of LHb neurons were excite, excitement and inhibition, excitatory response. While we excited LHb, LPO neurons showed inhibitory effect, suggesting that the function LHb and LPO was close contact and mutual influence, which may form a negative feedback loop involved in the regulation of sleep.3. With six hours of sleep deprivation in animals, lesion of the LHb rats showed increased wake time, NREMS was increased and detla activity was increased, as well as the lower theta wave. Lateral habenular nucleus microinjection of retrograde tracer (CTb), after 3 hours of sleep deprivation showed more c-fos + and CTb + double-stained cells in LPO in the SD group compared with normal sleep group. It suggested that LPO - LHb participate in the regulation of sleep-wakefulness cycle, to increase of sleep depth and propensity, which is related to these two parts involved in the regulation of recovery sleep after sleep deprivation.Our study found that the lateral habenular nucleus is a new center in sleep-promoting, not only regulating the total amount of sleep and regulating depth and propensity. More importantly, defined the LPO– LHb constitute a negative feedback pathway in regulating sleep, but it is not very clear that mechanisms between the two nuclei regulation sleep. In the future Research we will carry out further exploration.
|
PDF Full Text Request