Study On The Distribution Of Dopamine Receptors In Paraventricular Nucleus And Locus Coeruleus And Their Projective Tracing From Substantia Nigra

BackgroundParkinson’s disease(PD)is a neurodegenerative disorder characterized by the degeneration of dopaminergic neurons in the substantia nigra(SN).In PD patients,resting tremor and panic gait are the main somatic motor symptoms.The data show that patients with PD have gastrospasm,constipation and other gastrointestinal dysfunction than somatic movement disorders several years earlier.The dorsal motor nucleus of vagus(DMV)is the main nuclear group that controls and regulates the movement of the stomach.The fibers of DMV can be distributed to the stomach and produce contraction and relaxation of the stomach.Autopsy reports that there are also neuronal degenerative changes in the DMV of PD patients.Our group found earlier: There are no neurons directly projected to the DMV in the SN but can be directly projected to the hypothalamus PVN and LC.Morphological data also showed that the locus coeruleus,lateral hypothalamic area and paraventricular nucleus(PVN)all have fibers projected to DMV.We believe that SN may form a neural pathway with DMV indirectly through PVN,LC,and lateral hypothalamic nucleus.The DA released by SN needs to bind with the DA receptor on the target cell.The DA receptor is divided into D1,D2,D3,D4,and D5.No dopamine receptor morphology is found in PVN and LC-related literature.In this study,the expression and distribution characteristics of five DA receptors in two nuclear groups of PVN and LC were studied.NV staining,immunofluorescence,and neurotracing were used to modulate DMV in SN neurons via PVN and LC.Then influence the gastric motility to provide morphological basis.ObjectivesTo study the distribution of dopamine receptors D1-D5 in PVN and LC,and their positional relationship with the SN dopaminergic nerve fibers projected onto both PVN and LC nuclei,indirectly regulating DMV activity by SN through PVN and LC.Provide morphological evidence.Methods1.Nissl staining: To determine the location of each nuclear group such as SN,PVN,and LC in the rat brain.2.Immunofluorescence: To explorethe expression and distribution of DA receptors in PVN and LC with confocal laser scanning microscopy.3.Neurograde antegrade tracing: BDA-GFP was injected into the bilateral SN of SD rats using a stereotaxic apparatus.After one week of feeding,the presence of BDA-labeled nerve fibers in PVN and LC was observed under a laser confocal microscope.The immunohistochemical double labeling technique was used to observe the localized relationship between the tracked nerve fibers and neurons expressing DA receptors.Results1.D1-D5 is widely expressed in PVN in normal rats but has a different distribution.Among them,the positive cells of D1 and D5 are the most widely distributed;D3 and D4 are the second;D2 receptors are the least distributed.Mainly located in the middle of PVN in the paraventricular nucleus small cell,lateral paraventricular nucleus large cell,paraventricular nucleus ventral and hypothalamic dorsolateral cap.2.D1-D5 is widely distributed in normal rat LC.Among them,the positive expression of D1 and D5 is the most widely distributed,and the distribution of D2 receptors is relatively small.On the coronal section,dopamine receptor-positive neurons were distributed in the LC in the form of a strip,close to the lateral wall of the fourth ventricle.3.After antegrade tracing of the BDA fluorescence tracer,a fluorescent trace of the aggregated BDA was observed within the SN nucleus to confirm successful injection.In the PVN and LC nuclei,a large number of filamentous BDA-positive fibers were observed by fluorescence microscopy.Further immunofluorescence staining of the D1 and D2 receptors in the BDA-GFP-survived region revealed that these green filamentous positive nerve fibers were mostly distributed around dopamine receptor-positive neurons.Conclusions1.DA receptors are distributed in PVN and LC.Among them,the D1 and D5 are the mostand D2 receptors were the least.2.2.Dopaminergic neurons in SN can directly project to PVN,LC,and surround the DA receptor-positive neurons,further clarifying the neural projections between SN and PVN and SN and LC.3.This study provides mopharologic evidences for the direct regulation of SN on PVN and LC,and indirect regulatory effects on DMV and gastric motility through PVN and LC.