General anesthesia is widely used in clinical practice,whereas the exact mechanism behind the general anesthetic-induced reversible loss of consciousness remains unclear.Recent studies have revealed a close relationship between the dopaminergic system and general anesthetic-induced loss of consciousness.This system,encompassing dopamine neurons,dopamine receptors,and related neural pathways,regulates functions such as movement,memory,arousal,and cognition.The dopaminergic neurons in the ventral periaqueductal gray and ventral tegmental area,along with D1 receptors,have been shown to facilitate emergence from anesthesia.However,the role of D2 receptors remains controversial.This review summarizes recent advancements in the role of the dopaminergic system in general anesthesia and the underlying mechanism,with the aim of clarifying the mechanism of general anesthesia and providing a theoretical basis for preventing delayed emergence from anesthesia.
Humans ; Anesthesia, General ; Brain/metabolism* ; Dopaminergic Neurons/physiology* ; Dopamine/physiology* ; Animals

OBJECTIVE: To observe the effects of electroacupuncture (EA) at "Shenting" (GV24) and "Baihui" (GV20) on mitochondrial autophagy in hippocampal neurons and silent information regulator sirtuin 1 (Sirt1)/forkhead box O3 (FOXO3)/PTEN-inducible kinase 1 (PINK1)/Parkin pathway in rats with learning-memory impairment after cerebral ischemia reperfusion injury. METHODS: A total of 35 male SD rats were randomly divided into a sham operation group (9 rats) and a modeling group (26 rats). In the modeling group, middle cerebral artery occlusion method was used to establish the middle cerebral artery ischemia-reperfusion (MCAO/R) model, and 18 rats of successful modeling were randomly divided into a model group and an EA group, 9 rats in each one. EA was applied at "Shenting" (GV24) and "Baihui" (GV20) in the EA group, 30 min a time, once a day for 14 days. After modeling and on 7th and 14th days of intervention, neurologic deficit score was observed; the learning-memory ability was detected by Morris water maze test; the morphology of neurons in CA1 area of hippocampus was detected by Nissl staining; the mitochondrial morphology was observed by transmission electron microscopy; the protein expression of Beclin-1, microtubule-associated protein 1 light chain 3B (LC3B), P62, Sitrt1, FOXO3, PINK1 and Parkin was detected by Western blot. RESULTS: After modeling, the neurologic deficit scores in the model group and the EA group were higher than that in the sham operation group (P<0.001); on 7th and 14th days of intervention, the neurologic deficit scores in the model group were higher than those in the sham operation group (P<0.001), the neurologic deficit scores in the EA group were lower than those in the model group (P<0.05, P<0.01). After modeling, the escape latency in the model group and the EA group was prolonged compared with that in the sham operation group (P<0.001); on 9th-13th days of intervention, the escape latency in the model group was prolonged compared with that in the sham operation group (P<0.001), the escape latency in the EA group was shortened compared with that in the model group (P<0.05, P<0.01, P<0.001). The number of crossing plateau in the model group was less than that in the sham operation group (P<0.001); the number of crossing plateau in the EA group was more than that in the model group (P<0.05). In the model group, in CA1 area of hippocampus, the number of neurons was less, with sparse arrangement, nuclear fixation, deep cytoplasmic staining, and reduction of Nissl substance; the morphology of mitochondrion was swollen, membrane structure was fragmented, and autophagic lysosomes were formed. Compared with the model group, in the EA group, in CA1 area of hippocampus, the number of neurons was increased, the number of cells of abnormal morphology was decreased, and the number of Nissl substance was increased; the morphology of mitochondrion was more intact and the number of autophagic lysosomes was increased. Compared with the sham operation group, in the model group, the protein expression of Beclin-1, FOXO3, PINK1, Parkin and the LC3BⅡ/Ⅰ ratio in hippocampus were increased (P<0.01, P<0.001), while the protein expression of P62 was decreased (P<0.05). Compared with the model group, in the EA group, the protein expression of Beclin-1, Sirt1, FOXO3, PINK1, Parkin and the LC3BⅡ/Ⅰratio in hippocampus were increased (P<0.001, P<0.01), while the protein expression of P62 was decreased (P<0.001). CONCLUSION EA at "Shenting" (GV24) and "Baihui" (GV20) can relieve the symptoms of neurological deficits and improve the learning-memory ability in MCAO/R rats, its mechanism may relate to the modulation of Sirt1/FOXO3/PINK1/Parkin pathway and the enhancement of mitochondrial autophagy.
Animals ; Electroacupuncture ; Male ; Rats, Sprague-Dawley ; Rats ; Forkhead Box Protein O3/genetics* ; Reperfusion Injury/metabolism* ; Ubiquitin-Protein Ligases/genetics* ; Brain Ischemia/complications* ; Mitochondria/genetics* ; Autophagy ; Protein Kinases/genetics* ; Sirtuin 1/genetics* ; Humans ; Memory Disorders/psychology* ; Signal Transduction

OBJECTIVE: To observe the effects of moxibustion at "Shenque" (CV8) on urodynamics and the expression of brain-derived neurotrophic factor (BDNF) and immediate early gene (c-fos) in pontine micturition center (PMC), periaqueductal gray (PAG), medial prefrontal cortex (mPFC) of neurogenic bladder (NB) rats after spinal cord injury. METHODS: Twenty-four SPF female SD rats were randomly divided into a sham-operation group (6 rats) and a modeling group (18 rats). In the modeling group, T₉ complete spinal cord transection method was used to establish a neurogenic detrusor overactivity model, and the 12 rats with successful modeling were randomized into a model group and a moxibustion group, with 6 rats in each group. The rats in the moxibustion group were treated with ginger/salt-insulated moxibustion at "Shenque" (CV8), and 4 consecutive moxa cones were delivered in one intervention. Moxibustion was operated once daily and for 14 days. After intervention completion, the urodynamic indexes of rats in each group were detected. Fluorescence quantitative PCR was used to detect the mRNA expression of BDNF and c-fos in PMC, PAG and mPFC in rats. Western blot was used to detect the protein expression of BDNF and c-fos in PMC, PAG and mPFC. RESULTS: The rats in the sham-operation group did not show phasic detrusor contraction during bladder filling. Compared with the model group, the frequency and amplitude of the phasic detrusor contraction were reduced 5 min before urine leakage in the rats of the moxibustion group (P<0.05), and the duration of the first phasic detrusor contraction during bladder filling was prolonged (P<0.05). Compared with the sham-operation group, the mRNA and protein expression of BDNF and c-fos in PMC, PAG and mPFC increased in the model group (P<0.05). Compared with the model group, the mRNA and protein expression of BDNF and c-fos in PMC, PAG and mPFC decreased in the moxibustion group (P<0.05). CONCLUSION Moxibustion at "Shenque" (CV8) can improve the phasic contraction during bladder filling in NB rats after spinal cord injury, possibly by down-regulating the mRNA and protein expression of BDNF and c-fos in PMC, PAG, and mPFC.
Animals ; Moxibustion ; Female ; Rats ; Brain-Derived Neurotrophic Factor/metabolism* ; Rats, Sprague-Dawley ; Acupuncture Points ; Spinal Cord Injuries/metabolism* ; Urinary Bladder, Neurogenic/etiology* ; Proto-Oncogene Proteins c-fos/metabolism* ; Humans ; Urinary Bladder/physiopathology* ; Brain/metabolism* ; Urination

OBJECTIVE: To observe the effects of Xingnao Kaiqiao acupuncture technique (for regaining consciousness and opening orifice) on methylation of N6-methyladenosine (m6A), and key methyltransferases and demethylases, so as to clarify the mechanism of acupuncture on cerebral ischemia-reperfusion injury (CIRI). METHODS: Of 68 male Sprague-Dawley rats of SPF grade, 15 rats were randomly selected as a sham-operation group, and the remaining rats were subjected to the model of middle cerebral artery occlusion using the suture ligation. CIRI was induced by ischemia for 2 h followed by reperfusion. Rats that failed to modeling or died were excluded. The rest 45 rats were randomly divided into three groups, i.e. model group, acupuncture group, and non-point acupuncture group, with 15 rats in each group. The rats in the acupuncture group were treated with acupuncture at bilateral "Neiguan" (PC6) and "Shuigou" (GV26). In the non-point acupuncture group, acupuncture was delivered at three non-points, located 3 mm below the bilateral midaxillary line and 3 mm lateral to the tip of the coccyx. One intervention was operated in these two acupuncture groups and the needles were retained for 30 min. Before modeling start and 2 h after ischemia, a laser speckle flowmeter was used to monitor the cerebral blood perfusion. In 2 h of ischemia and 24 h of reperfusion, the neurological behavioral score was evaluated. The volume of rat cerebral infarction was determined by triphenyltetrazolium chloride (TTC) staining, and the level of m6A methylation in ischemic cortical area was detected by Dot blot, and the protein and mRNA expression of the demethylase i.e. fat mass and obesity-associated protein (FTO), AlkB homolog 5 (ALKBH5) and key methyltransferases, i.e. methyltransferase-like 3 (METTL3), methyltransferase-like 14 (METTL14), and Wilms' tumor 1-associated protein (WTAP) in ischemic cortical area were detected by Western blot and real-time PCR. RESULTS: Cerebral blood perfusion decreased by>70% after 2 h ischemia. Compared with the sham-operation group, the neurobehavioral score and the percentage of cerebral infarction volume increased in the model group (P<0.01); the level of m6A methylation in the ischemic cortical area increased (P<0.01), the protein and mRNA expression of FTO decreased (P<0.01), and that of ALKBH5, METTL3, and METTL14 increased (P<0.01, P<0.05) in the model group. When compared with the model group and the non-point acupuncture group, the acupuncture group showed a decrease in the neurobehavioral score and the percentage of cerebral infarction volume (P<0.01), the level of m6A methylation in the ischemic cortical area was reduced (P<0.01, P<0.05), and the protein and mRNA expression of FTO was elevated (P<0.01). CONCLUSION Xingnao Kaiqiao acupuncture technique presents its protective effect on the brain in the rats with CIRI, which is related to up-regulating the expression of FTO and modulating m6A methylation.
Animals ; Rats, Sprague-Dawley ; Male ; Acupuncture Therapy ; Reperfusion Injury/genetics* ; Rats ; Brain Ischemia/genetics* ; Humans ; Adenosine/metabolism* ; Methylation ; Acupuncture Points ; Cerebral Cortex/metabolism*

OBJECTIVE: To explore the neuroprotective effect and underlying mechanism of Xingnao Kaiqiao acupuncture (acupuncture for regaining consciousness and opening orifices) in the rat models of cerebral ischemia-reperfusion injury (CIRI) based on the p53 protein (p53)/solute carrier family 7 member 11 (SLC7A11)/glutathione peroxidase 4 (GPX4) signaling pathway. METHODS: Of 102 male Wistar rats, 20 rats were randomly collected as a sham-operation group. Using a modified external carotid artery filament insertion method, CIRI models were prepared by occluding the middle cerebral artery in the rest rats. After modeling and excluding 1 non-successfully modeled rat and 1 dead one, the other modeled rats were randomized into a model group, an agonist group, an acupuncture group, and an acupuncture + agonist group, 20 rats in each one. Xingnao Kaiqiao acupuncture therapy was delivered in the rats of the acupuncture group and the acupuncture + agonist group. The acupoints included "Shuigou" (GV26), bilateral "Neiguan" (PC6), and "Sanyinjiao" (SP6) on the affected side. Electroacupuncture was attached to "Neiguan" (PC6) and "Sanyinjiao" (SP6) on the affected side, with dense-disperse wave, a frequency of 2 Hz/15 Hz and intensity of 1 mA. The intervention was delivered twice daily, 20 min each time and for 7 consecutive days. In the agonist group and acupuncture+agonist group, p53 agonist, COTI-2 was intraperitoneally injected (15 mg/kg), once daily for 7 consecutive days. Neurological deficit was evaluated using Zausinger's six-point scale. Cerebral infarction volume was quantified by triphenyl tetrazolium chloride (TTC) staining. Histopathological changes were observed using hematoxylin-eosin (HE) staining. Iron deposition was assessed by Prussian blue staining. Mitochondrial ultrastructure in the ischemic cortex was examined under transmission electron microscopy (TEM). Serum iron (Fe²⁺) was measured with chromometry. Malondialdehyde (MDA) and glutathione (GSH) levels in the ischemic hippocampus were determined using thiobarbituric acid and microplate assays, respectively. The mean fluorescence intensity of reactive oxygen species (ROS) in the ischemic cortex was analyzed by flow cytometry. The mRNA and protein expression of GPX4, SLC7A11, and p53 in the ischemic hippocampus were evaluated using quantitative real-time PCR (qRT-PCR) and Western blotting, respectively. RESULTS: Compared with the sham-operated group, the model group exhibited the decrease in neurological deficit score (P<0.01), and the increase in cerebral infarction volume percentage (P<0.01). The changes of brain tissue were presented in extensive cellular necrosis, pyknotic and deeply-stained nuclei, and vacuolar degeneration. The iron deposition was elevated in cortex and hippocampus (P<0.01), mitochondrial membrane density increased, the cristae was broken or reduced, and the outer membrane ruptured. The levels of Fe²⁺ and MDA, as well as the mean flourscence intensity of ROS were elevated (P<0.01) and the level of GSH was reduced (P<0.01). The mRNA and protein expression of GPX4 and SLC7A11 was reduced (P<0.01), while that of p53 rose (P<0.01). When compared with the model group, in the agonist group, the neurological deficit score was reduced (P<0.05), the percentage of infarction volume was higher (P<0.01), the histopathological damage was further exacerbated, and the percentage of iron deposition increased in the cortex and hippocampus (P<0.01). The mitochondrial quantity decreased, the membrane density increased, the mitochondrial cristae were broken or reduced, and the outer membrane was ruptured. The levels of Fe²⁺ and MDA, as well as the mean flourscence intensity of ROS were higher (P<0.01, P<0.05) and the level of GSH was reduced (P<0.05). The mRNA and protein expression of GPX4 and SLC7A11 decreased (P<0.01, P<0.05), while that of p53 was elevated (P<0.01). Besides, in comparison with the model group, the neurological deficit score was higher in the acupuncture group and the acupuncture + agonist group (P<0.01, P<0.05), the percentage of cerebral infarction volume was lower in the acupuncture group (P<0.01), the pathological damage of brain tissue was alleviated in the acupuncture group and the acupuncture + agonist group, and the percentage of iron depositiondecreased in the cortex and hippocampus (P<0.01). The mitochondrial structure was relatively clear, the mitochondrial cristae were fractured or reduced mildly in the acupuncture group and the acupuncture + agonist group. The levels of Fe²⁺ and MDA, as well as the mean flourscence intensity of ROS were lower (P<0.01) and the level of GSH was higher (P<0.01) in the acupuncture group. The mean fluorescence intensity of ROS were dropped (P<0.01) in the acupuncture + agonist group. The mRNA expression of GPX4 and SLC7A11 was elevated (P<0.01) and that of p53 was reduced (P<0.01, P<0.05) in either the acupuncture group or the acupuncture + agonist group; the protein expression of GPX4 and SLC7A11 rose (P<0.05, P<0.01) and that of p53 was dropped (P<0.01) in the acupuncture group; and the protein expression of p53 was also lower in the acupuncture + agonist group (P<0.05). When compared with the agonist group, in the acupuncture + agonist group, neurological deficit score increased (P<0.01), the percentage of cerebral infarction volume decreased (P<0.01), the pathological brain tissue damage was reduced, the percentage of iron deposition in cortex and hippocampus decreased (P<0.01), the mitochondrial structure was relatively clear and the cristae broken or reduced slightly; the levels of Fe²⁺ and MDA, as well as the mean fluorescence intensity of ROS were dropped (P<0.01), while the level of GSH increased (P<0.05); the mRNA and protein expression of GPX4 and SLC7411 was elevated (P<0.01, P<0.05), and that of p53 reduced (P<0.01). In comparison with the acupuncture + agonist group, in the acupuncture group, the neurological deficit score increased (P<0.05), the percentage of cerebral infarction volume decreased (P<0.05), the pathological brain tissue damage was alleviated, the percentage of iron deposition in cortex and hippocampus decreased (P<0.01), the mitochondrial structure was normal in tendency; the levels of Fe²⁺ and MDA, as well as the mean fluorescence intensity of ROS were reduced (P<0.05), while the level of GSH rose (P<0.01); the mRNA and protein expression of GPX4 and SLC7411 was elevated (P<0.01, P<0.05), and that of p53 reduced (P<0.01, P<0.05). CONCLUSION Xingnao Kaiqiao acupuncture can alleviate neurological damage in CIRI rats, which is obtained probably by inhibiting ferroptosis through p53/SLC7A11/GPX4 pathway.
Animals ; Reperfusion Injury/metabolism* ; Male ; Acupuncture Therapy ; Rats ; Tumor Suppressor Protein p53/genetics* ; Brain Ischemia/metabolism* ; Rats, Wistar ; Signal Transduction ; Humans ; Phospholipid Hydroperoxide Glutathione Peroxidase/genetics* ; Disease Models, Animal ; Acupuncture Points ; Amino Acid Transport System y+/genetics*

Neurological diseases are a major health concern, and brain injury is a typical pathological process in various neurological disorders. Different biomarkers in the blood or the cerebrospinal fluid are associated with specific physiological and pathological processes. They are vital in identifying, diagnosing, and treating brain injuries. In this review, we described biomarkers for neuronal cell body injury (neuron-specific enolase, ubiquitin C-terminal hydrolase-L1, αII-spectrin), axonal injury (neurofilament proteins, tau), astrocyte injury (S100β, glial fibrillary acidic protein), demyelination (myelin basic protein), autoantibodies, and other emerging biomarkers (extracellular vesicles, microRNAs). We aimed to summarize the applications of these biomarkers and their related interests and limits in the diagnosis and prognosis for neurological diseases, including traumatic brain injury, status epilepticus, stroke, Alzheimer's disease, and infection. In addition, a reasonable outlook for brain injury biomarkers as ideal detection tools for neurological diseases is presented.
Humans ; Biomarkers/cerebrospinal fluid* ; Nervous System Diseases/diagnosis* ; Brain Injuries/metabolism* ; Phosphopyruvate Hydratase/cerebrospinal fluid* ; Glial Fibrillary Acidic Protein/blood* ; S100 Calcium Binding Protein beta Subunit/blood* ; tau Proteins/cerebrospinal fluid* ; Ubiquitin Thiolesterase/blood* ; Myelin Basic Protein/cerebrospinal fluid* ; Neurofilament Proteins/blood* ; MicroRNAs/blood* ; Brain Injuries, Traumatic/metabolism*

Gliomas are the most common primary neuroepithelial tumors of the central nervous system in adults, of which glioblastoma is the deadliest subtype. Apart from the intrinsically indestructible characteristics of glioma (stem) cells, accumulating evidence suggests that the tumor microenvironment also plays a vital role in the refractoriness of glioblastoma. The primary functions of platelets are to stop bleeding and regulate thrombosis under physiological conditions. Furthermore, platelets are also active elements that participate in a variety of processes of tumor development, including tumor growth, invasion, and chemoresistance. Glioma cells recruit and activate resting platelets to become tumor-educated platelets (TEPs), which in turn can promote the proliferation, invasion, stemness, and chemoresistance of glioma cells. TEPs can be used to obtain genetic information about gliomas, which is helpful for early diagnosis and monitoring of therapeutic effects. Platelet membranes are intriguing biomimetic materials for developing efficacious drug carriers to enhance antiglioma activity. Herein, we review the recent research referring to the contribution of platelets to the malignant characteristics of gliomas and focusing on the molecular mechanisms mediating the interaction between TEPs and glioma (stem) cells, as well as present the challenges and opportunities in targeting platelets for glioma therapy.
Humans ; Glioma/metabolism* ; Blood Platelets/physiology* ; Brain Neoplasms/pathology* ; Tumor Microenvironment

Inflammatory bowel disease (IBD) is an idiopathic intestinal inflammatory condition with chronic and relapsing manifestations and is characterized by a disturbance in the interplay between the intestinal microbiota, the gut, and the brain. The microbiota-gut-brain axis involves interactions among the nervous system, the neuroendocrine system, the gut microbiota, and the host immune system. Increasing published data indicate that psychological stress exacerbates the severity of IBD due to its negative effects on the microbiota-gut-brain axis, including alterations in the stress response of the hypothalamic-pituitary-adrenal (HPA) axis, the balance between the sympathetic nervous system and vagus nerves, the homeostasis of the intestinal flora and metabolites, and normal intestinal immunity and permeability. Although the current evidence is insufficient, psychotropic agents, psychotherapies, and interventions targeting the microbiota-gut-brain axis show the potential to improve symptoms and quality of life in IBD patients. Therefore, further studies that translate recent findings into therapeutic approaches that improve both physical and psychological well-being are needed.
Humans ; Inflammatory Bowel Diseases/metabolism* ; Stress, Psychological/microbiology* ; Gastrointestinal Microbiome/physiology* ; Brain/metabolism* ; Hypothalamo-Hypophyseal System ; Pituitary-Adrenal System ; Animals

Ischemic stroke (IS) ranks as a leading cause of death and disability globally. The blood-brain barrier (BBB) poses significant challenges for effective drug delivery to brain tissues. Recent decades have seen the development of targeted nanomedicine and biomimetic technologies, sparking substantial interest in biomimetic drug delivery systems for treating IS. These systems are devised by utilizing or replicating natural cells and their derivatives, offering promising new pathways for detection and transport across the BBB. Their multifunctionality and high biocompatibility make them effective treatment options for IS. In addition, the incorporation of engineering techniques has provided these biomimetic drug delivery systems with active targeting capabilities, enhancing the accumulation of therapeutic agents in ischemic tissues and specific cell types. This improvement boosts drug transport and therapeutic efficacy. However, it is crucial to thoroughly understand the advantages and limitations of various engineering strategies employed in constructing biomimetic delivery systems. Selecting appropriate construction methods based on the characteristics of the disease is vital to achieving optimal treatment outcomes. This review summarizes recent advancements in three types of engineered biomimetic drug delivery systems, developed from natural cells and their derivatives, for treating IS. It also discusses their effectiveness in application and potential challenges in future clinical translation.
Humans ; Drug Delivery Systems/methods* ; Ischemic Stroke/drug therapy* ; Animals ; Blood-Brain Barrier/metabolism* ; Stroke/drug therapy*

BACKGROUND: Changes in N-terminal pro-B-type natriuretic peptide (NT-proBNP) levels may not fully translate into patient-reported health status in patients with heart failure (HF). We aimed to evaluate the correlation between NT-proBNP levels and patient-reported health status changes at one month after discharge of patients, and their associations with risk of death and rehospitalization in patients with acute HF. METHODS: We used data from the China Patient-centered Evaluative Assessment of Cardiac Events Prospective Heart Failure Study (PEACE 5p-HF Study). Patient-reported health status was measured by the 12-item Kansas City Cardiomyopathy Questionnaire (KCCQ-12). Patients who were hospitalized for HF and completed the KCCQ-12 and NT-proBNP tests before and one month after discharge were eligible in our study. We stratified patients into different groups based on NT-proBNP levels (i.e., improved, stable, and deteriorated) and KCCQ-12 scores (i.e., not deteriorated and deteriorated). We also examined the associations of the joint NT-proBNP and KCCQ-12 change with the risk of one-year and four-year clinical outcomes. RESULTS: A total of 2461 patients were included in the analysis. The mean age was 64.06 ± 13.51 years, and 36.37% (895/2461) of the study population were female. Among patients with improved NT-proBNP levels, 115 (10.95%) patients had deteriorated KCCQ-12 scores. The correlation between the change in the KCCQ-12 score and NT-proBNP level was weak ( r2 = 0.002, P = 0.013). Stratification by changes in the KCCQ-12 score revealed subgroups with distinctive risks, such that patients with deteriorated KCCQ-12 scores in any of the NT-proBNP change groups exhibited an increased risk of one-year all-cause death than participants with not deteriorated KCCQ-12 scores in any of the NT-proBNP change groups. Patients with improved NT-proBNP levels and deteriorated KCCQ-12 scores presented greater risks of one-year all-cause death (hazard ratio [HR]: 2.45, 95% confidence interval [CI]: 1.34-4.48) than patients with stable NT-proBNP levels and not deteriorated KCCQ-12 scores (HR [95% CI], 1.77 [1.25-2.53]). CONCLUSIONS: A discrepancy between changes in NT-proBNP levels and KCCQ-12 scores was common. The change in NT-proBNP levels was not sufficient to characterize critical aspects related to HF during one month after discharge of patients. Changes in the KCCQ-12 score exhibit complementary information to NT-proBNP levels for the prediction of clinical outcomes in patients with acute HF. REGISTRATION www.clinicaltrials.gov (No. NCT02878811).
Aged ; Female ; Humans ; Male ; Middle Aged ; Health Status ; Heart Failure/metabolism* ; Natriuretic Peptide, Brain/metabolism* ; Peptide Fragments/metabolism* ; Prospective Studies