(m)VD-Hpα Promotes NREM Sleep And Antagonizes Anxiety-like Behavior And Sleep Disorder Via CB1 Cannabinoid Receptor

Disturbed sleep is a common clinical manifestation of individuals with anxiety patients,sleep disorder caused increased anxiety symptoms.Generally,sleep disorder and anxiety disorder are comorbid condition,they are related to each other in a bidirectional way.Cannabinoids involve in a variety of physiological regulations through acting on CB1 and CB2 cannabinoid receptors,such as sleep-wake state,olfactory function,emotion,reward,learning and memory.（m）VD-hemopressin（α）（（m）VD-Hpα）,a newly identified peptide derived fromα1 chain of hemoglobin,is presumed as a selectively agonist of CB1 receptor to to regulate pain,feeding,memories and blood pressure.However,it is unclear that whether（m）VD-Hpαis involved in the regulation of sleep-wake state,anxiety-like behaviour and sleep.Methods:In the first part of present study,the polysomnographic recording（20:00-20:00 h）including electroencephalogram（EEG）and electromyogram（EMG）and sleep-wake states analysis were employed to evaluate the effect of（m）VD-Hpαin sleep-wake states.CB1 receptor antagonist AM251 or CB2 receptor antagonist AM630 injected with（m）VD-Hpα,and CB1 receptor agonist WIN55,212-2 as a positive control were utilized to assess whether（m）VD-Hpαacts on CB1 receptor.The second part study,yohimbine（YO）,anα₂ receptor antagonist,was intraperitoneally injected to induce anxiety-like behaviour.Open field test（OFT）,elevated plus maze（EPM）,light/dark box（LDB）,marble-buring behaviors（MMB）,the polysomnographic recording（8:00-8:00 h）and sleep-wake states analysis were employed to evaluate the effect of（m）VD-Hpαon YO-induced anxiety-like behaviour and sleep.Immunohistochemistry of c-Fos was performed to remark the activated neurons induced by（m）VD-Hpα.Result:（m）VD-Hpα（20.1 nmol,i.c.v.）administration decreased REM sleep latency,and increased NREM sleep for 2 hours.The increased NREM sleep was due to extended episode duration.（m）VD-Hpα（6.7,13.4 nmol,i.c.v.）administration had no significant effect on sleep-wake state.The effects of（m）VD-Hpαon sleep-wake state could be blocked by AM251 instead of AM630.WIN55,212-2 decreased NREM and REM sleep latency,and increased NREM sleep at the first hour after administration by increasing the number of sleep segments.YO induced anxiety-like behavior,which was characterized by diminishing the time spent in center area and increasing the time spent in grooming in OFT;reducing the percentage of entries and time in EPM;decreasing the residence time in LDB;increasing buried bead number in MBB.（m）VD-Hpαantagonized anxiety-like behavior caused by YO,which could be blocked by co-injection of AM251.YO increased the sleep latency of NREM and REM sleep,reduced NREM sleep of the first hour after the treatment.REM sleep was suppressed for 4 hours.The decrease in NREM sleep was due to reduce the episode average duration of NREM sleep.（m）VD-Hpαaltered YO-induced sleep-wake pattern through shortening latency of NREM sleep and increasing NREM sleep via increasing the fragment average duration of NREM sleep,but it had no significant effect on the REM sleep.AM251could blocked the effect of（m）VD-Hpα.（m）VD-Hpαincreased the number of Fos immunoreactive（-ir）neurons in the central amygdala（CeA）and the dorsolateral periaqueductal gray（dlPAG）,decreased the number of Fos-ir in the basolateral amygdala（BLA）and locus coeruleus（LC）.Conclusion:（m）VD-Hpαpromotes NREM sleep and antagonizes anxiety behavior and sleep disorders through activating CB1 receptors;（m）VD-Hpαcauses an increase of Fos-ir number in CeA and dlPAG,and a decrease of Fos-ir number in BLA and LC,suggesting that（m）VD-Hpαpromotes NREM sleep and antagonizes anxiety behavior and sleep disorders possibly via CB1 receptor to act on the neurons in BLA,CeA,dlPAG and LC.