| Objective:Nonhuman primates are similar with humans in the tissue structure and biochemistry. Therefore, the study of their physiological function, biochemistry, pathophysiology and other aspects is important and meaningful in understanding the human physiology and diseases. The studies of magnetic resonance spectroscopy(MRS) and functional magnetic resonance imaging(fMRI) on rats and rabbits have been numerously reported, but this kind of studies on nonhuman primates are relatively rare.1. MRS, based on chemical shift theory, is a noninvasive imaging technique used in studying the normal or pathophysiological changes and making quantitative analysis of metabolites. This study firstly aims to explore the application of MRS in experimental studies on normal macaca fascicularis and to get basic data as a reference for further study of pathological conditions.2. Acupuncture represents one of the oldest and still widely used treatments. The second aim of this study was to detect the fMRI signal changes evoked by acupuncture stimulation on nonhuman primates and to explore the functional localization and its distributing orderliness of the central nervous system(CNS) reactions on acupuncturing the left and right acupoints of Zusanli(ST36) and a false acupoint near the left acupoint of Zusanli respectively, and then to offer reference for future research of both human and nonhuman primates.3. As an important sensory function, olfaction has been studied on the mechanism, such as its transmission, the functional localization and molecular biology. The studies of fMRI evoked by olfaction stimulation on human have been reported, but study on nonhuman primates has not been seen. The third aim of the study is to explore the fMRI signal changes evoked by olfaction stimulation on nonhuman primates.Materials and methods:1. Research objects and MR scanner6 healthy macaca fascicularis, which belong to the genus Macaca, family Cercopithecidae, order Primates, were selected in the study. MR examinations were performed with a quadrature knee joint coil at 3.0T MR scanner, with gradient strength of 40mT/m, gradient switching rate of 150mT/m/ms. All monkeys were anesthetized with ketamine and chloral hydrate before MR scanning.2. Method of MRSProton Brain Exam-Single Voxel(PROBE-SV) using a Point Resolved Spectroscopy Sequence(PRESS) was employed for MRS scanning, and four ROIs were selected in the axial image(the corpus striatum, frontal cortex, thalamus and cerebellum, with the size of 15mm×l5mm×l0mm, avoiding the contamination of the adjacent skull and cerebrospinal fluid). The regions around the ROI were all saturated accordingly. MRS scanning was repeated 3 times. N-acetylaspartate (NAA), creatine (Cr), choline (Cho) and the ratio of NAA/Cr, Cho/Cr were measured respectively. SPSS13.0 software and pairwise comparison were used for data analysis and p<0.05 was considered statistically significant.3. study design for acupuncture fMRIFMRI scannings during acupuncture stimulation at the left acupoint of Zusanli(ST36), the right Zusanli and the area beside the left Zusanli were performed respectively. The block design of the acupuncture stimulation was "rest-stimulation-rest". Each time,128 phases scanning was obtained. No acupuncture stimulation was performed during rest period and acupuncture stimulation was performed during stimulation period. The first 8 phases scanning was in rest period, subsequently every 10 phases scanning was regarded as a block in stimulation or rest period alternately all of that 100 phases. The acupuncture stimulation was performed by an experienced acupuncture physician. The acupoint position was decided based on the proportion of the shapes of human and macaca fascicularis. The acupuncture technique was "pingbupingxie".4. study design for olfaction fMRIFMRI scannings during alcohol and acetum scent stimulation were performed respectively. The block design was "rest-stimulation-rest". The monkey inhaled the air mixed with alcohol or acetum in stimulation period, while in rest period the monkey inhaled pure air.The fMRI protocol was the same as acupuncture fMRI. The stimulations were performed by the same two physicians.5. fMRI scanning parametersFLAIR T1WI and fMRI-BOLD(blood oxygenation level dependent) sequence were performed and 16 slices axial images of the entire brain paralleled to the AC-PC line were obtained. FLAIR T1WI axial images were used as the scout image for BOLD. GRE-EPI sequence was used in BOLD scanning.128 phases scanning were performed and 2048 images were obtained.6. fMRI data analysisData were analyzed by using Statistical Parametric Mapping software-SPM2 implemented in Matlab 7.0.1. The operation process included 10 steps, such as deleting the first 8 phases rest period images, conversion images format, realigning images, removing scalp, normalizing images, fMRI designing and estimating, etc. The outcome was superposed on axial images at last. Through normalizing step, the data were normalized in a standard space template of a macaca fascicularis(Washington University School of Medicine, St. Louis, MO).Random effect mode group analysis was applied in estimating and calculating with one sample t-test for group evoking in a certain stimulation and two sample t-test for the comparison between two stimulations. The test standard p<0.05 and the extent threshold 10 voxels were selected.Results:1. results of MRSNAA/Cr ratios ordering from maximum to minimum were halamus, cerebellum, frontal lobe, corpus striatum. Among them, thalamus and the other three structures were statistically different (p<0.05), the cerebellum and striatum were statistically different (p<0.05). Cho/Cr ratios ordering from maximum to minimum were as follows:frontal lobe, cerebellum, thalamus, striatum. There was significant difference between striatum and frontal cortex, striatum and cerebellum respectively(p<0.05).2. fMRI of acupuncture stimulationAcupuncture stimulation at the left acupoint of Zusanli increased BOLD signal in left precentral gyrus, right postcentral gyrus and temporal lobe, bilateral insula and precuneus. The strongest activation appeared in the right superior temporal gyrus. Deactivation pattern was observed in frontal lobe, parietal lobe, occipital lobe and cingulate gyrus. The obvious deactivation was seen in the right precentral gyrus.The average brain activations evoked by acupuncture stimulation at the right Zuanli were in bilateral insula and postcentral gyrus, right precentral gyrus, thalamus, temporal lobe and cerebellum. The strongest activation was in right superior temporal gyrus. While the deactivations in bilateral frontal lobe, parietal lobe, occipital lobe and cingulate gyrus were observed.Activation pattern of acupuncture stimulation at the nonacupoint beside the left Zusanli was obtained in the right postcentral gyrus, bilateral superior temporal gyri and precuneus. The strongest activation was in the right postcentral gyrus. At the same time, the deactivation pattern was observed in bilateral cingulate gyri, the left prefrontal gyrus and postcentral gyrus, the right lenticular nucleus, pons and midbrain. The obvious signal decrease was observed in the right lenticular nucleus.Two sample t-test between the activations of acupuncture stimulation at the left and the right acupoint of Zusanli was performed. In bilateral insula and precuneus, right temporal lobe and postcentral gyrus, left precentral gyrus, right lenticular nucleus and thalamus, midbrain, the activation was stronger at left Zusanli stimulation. Whereas, the stronger activation in bilateral frontal lobes, parietal lobes, cingulate gyri and temporal lobes were observed by stimulating the right Zusanl.The difference between the deactivation patterns of acupuncture stimulation at the left acupoint of Zusanli and the right one was observed. Stronger deactivations in right thalamus, bilateral frontal lobes, parietal lobes and temporal lobes were observed during left Zusanli acupuncture stimulation. While stronger deactivations in bilateral prefrontal gyri, postcentral gyri, thalamus, lenticular nucleus, insula, precuneus, and the right temporal lobe were recorded by the right Zusanli stimulation.Through two sample t-test between the activations in acupuncturing the left Zusanli and the nonacupoint beside the left Zusanli, the stronger activations in left precentral gyrus, bilateral precuneus, right temporal lobe, thalamus and lenticular nucleus, corpus callosum were observed by stimulating the left Zusanli. Whereas, the stronger activations in parietal lobe, frontal lobe, right temporal lobe, left precuneus were observed by stimulating the nonacupoint.The difference between the deactivation patterns of acupuncture stimulating at the left Zusanli and the nonacupoint beside the left Zusanli was observed as follows:there were stronger deactivations in bilateral precentral gyri and postcentral gyri, the left frontal lobe, temporal lobe and precuneus, the right thalamus by the left Zusanli stimulation. While stronger deactivations in bilateral precentral lobe, precuneus, right lenticular nucleus and temporal lobe, midbrain and the left frontal lobe were observed by the nonacupoint stimulation.3. results of fMRI by olfaction stimulationDuring olfaction fMRI examination, the respiration depth and frequency of the monkeys decreased evidently in scent stimulation period, while resumed to normal when pure air inhaled.When acetum scent stimulation was given, increased BOLD signal was observed in bilateral paracentral lobules, cingulate gyri, left frontal lobe, temporal lobe and lingual gyrus, thalamus, right insula and lenticular nucleus. Deactivation pattern was observed in cingulate gyrus, left paracentral lobule, lenticular nucleus and lingual gyrus.The average brain activations evoked by alcohol scent stimulation were in bilateral paracentral lobules, cingulate gyri, left temporal lobe and frontal lobe, right lenticular nucleus, midbrain and cerebellum. While the deactivations were observed in bilateral paracentral lobules, cingulate gyri and precentral gyri, the left frontal lobe, bilateral caudate nucleus and lenticular nucleus and cerebellum.Through two sample t-test between the activations of the acetum scent and the alcohol scent, the stronger activations in bilateral cingulate gyri, right thalamus, the posterior part of lenticular nucleus were observed by acetum stimulation. The stronger activations in left paracentral lobule, the bilateral anterior parts of lenticular nucleus were observed by alcohol scent stimulation.The difference between the deactivation patterns of the acetum and the alcohol scent stimulation was observed as follows:there were stronger deactivations in right cingulate gyrus, the anterior part of the right lenticular nucleus, the medial part of the left lenticular nucleus by acetum stimulation. And stronger deactivations in the right caudate nucleus and lenticular nucleus, left thalamus and cingulate gyrus were shown by alcohol stimulation.Conclusion:1. The results show that MRS study of the brain of nonhuman primates is feasible. The NAA/Cr ratio of hypothalamus is higher than that of the cerebellum, frontal lobe and striatum. NAA/Cr ratio of the cerebellum is higher than that of the striatum. The Cho/Cr ratio of frontal lobe is higher than that of the striatum, and the Cho/Cr ratio of cerebellum is higher than that of the striatum. The MRS examination of nonhuman primates can accurately reflect the difference between brain structures and metabolites.2. Different areas in brain of nonhuman primates present activation or deactivation during acupuncture stimulation at the left acupoint of Zusanli, right Zusanli and the nonacupoint area beside the left Zusanli. According to the activation pattern, there might be a compact relation between acupuncture and precentral gyrus, insula and temporal lobe. The acupuncture at acupoint of Zusanli can induce extensive deactivation. And the deactivation of cingulate gyrus maybe presents an important role to understand and explain the mechanism of acupuncture, acupuncture anesthesia and acupuncture analgesia. There is a signifinant difference between the activations of acupuncture acupoint and nonacupoint.3. BOLD activation and deactivation all can be observed by using scent stimulation. Frontal and temporal lobe can activate as the nerve center of olfaction. The central reaction induced by scent stimulation has an affinity with paracentral lobule, cingulate gyrus and lenticular nucleus. |
PDF Full Text Request