The Mechanism Study On Rest-activity And Sleep-waking Circadian Dysfunction In Parkinsonian Rats

Parkinson’s disease (PD) is a progressive neurodegenerative disorder, resultedfrom the death of dopamine-generating cells in the substantia nigra, a region of themidbrain. The pathology of PD is characterized by Lewy bodies in neurons, theaccumulation of alpha-synuclein into inclusions. Major clinical features aremovement disorders, including tremor, rigidity, brady kinesia, postural instability, etc.and non-movement-related symptoms including psychiatric disorders, emotionaldisorders, circadian dysfunction, and autonomic dysfunction. Circadian dysfunctions,especially sleep disorders, are very common in PD patients, which usually bringheavy burden on them. Recently, PD related sleep disorders is paid more and moreconcern in PD research.Purpose: The rest-activity rhythm and sleep-waking circadian changes wereobserved and PD-related nuclei’s function in non-movement-related symptoms wereinquired in PD rats. It will be helpful to illuminate the possible pathogenesis of PDand to provide powerful evidence for PD diagnosis and treatment.Methods:60male Wistar rats were used and divided randomly into2groups,sham group and PD group. Parkinsonian rat models were made by6-OHDA injectioninto unilateral medial forebrain bundle (mfb).(1) Rest-activity rhythm changes wereobserved by behavioral exam, running free-wheel;(2) EEG and EMG was recordedvia neurophysiological techniques to study sleep-waking discharges;(3) TH-positiveneurons in substantia nigra, compact part (SNC) were measured throughimmunohistochemical method;(4) Cytochrome C oxidase (COX) activity wasmeasured in lateral habenula (LHb), locus coeruleus (LC), dorsal raphe nucleus(DRN), laterodorsal tegmental nucleus (LDT) by immunohistochemical method;(5)5-HT level was monited in DRN by high-performance liquid chromatography (HPLC);(6) Circadian rhythm related gene, Per2mRNA expression was detected in SNC and LHb by real-time quantitative PCR.Results:(1) Daily basic rest-activity rhythm was kept well in PD rats, butmovement rhythm was changed with significantly decreased in running free-wheel,both in daytime and night (P<0.0001);(2) There are alternations in sleep-wakingcycle in PD rats, including total sleeping time increase and total waking timereduction. Among these changes, REMS decreased significantly during ZT0-ZT5(P<0.05), and NREMS increased significantly during ZT6-ZT11(P<0.05);(3)TH-positive neurons decrease significantly in SNC (P<0.05);(4) COX activitydecreased in neurons of LC, LDT and DRN (P<0.05, P<0.001, P<0.001, respectively)and increased in neurons of LHb (P<0.05);(5) The normal secretion rhythm of5-HTin DRN was disturbed.5-HT level decreased to the minimum at ZT06(P<0.001);(6)There was no changes of circadian rhythm related gene, Per2mRNA expression inSCN and LHb at each time point (P>0.05).Conclusion:(1) The circadian dysfunction of rest-activity and sleep-wakingcycle were confirmed in PD rats.5-HT secretion disturbance seems to be involved in.(2) Several regions of brainstem may play roles on the development of circadiandysfunctions in PD, including SCN, LHb, DRN, LC, LDT, etc.