The Expression Of 5-HT And 5-HT_2AR In The Anterior Thalamic Nuclei Of Rat

Objective:to explore the expression of 5-HT and 5-HT2AR in the anterior thalamic nuclei (ATN) of Sprague-Dawley (SD) rat. and to understand the possible roles of them in learning and memory. From a protein level for them to provide the morphological basis.Methods:Animal SD adult rats 16 (light microscope group 10, electron microscope group 6), Male, weight 200-250g. By the Experimental Animal Center of Dalian Medical University,4%chloral hydrate intraperitoneal anesthesia (1ml/100g body weight), exposed the heart, under direct vision to the left ventricular perfusion needle inserted into the ascending aorta,Cut the right atrial appendage, rapid infusion 200ml saline solution until colorless right atrial appendage outflow. Reperfusion fixative 4%paraformaldehyde (pH7.4) 300ml (electron microscopy specimens with a 4%-0.5%glutaraldehyde paraformaldehyde mixture of 300ml),rapid infusion 100ml, after the slow infusion 200ml, continuous infusion of about 2h. Completed immediately by filling the brain, removed the brain surface of the meninges, and placed in fresh fixative, the fixed overnight at 4℃. Finally, continuous vibration microtome coronal slices, slice thickness of 30μm (electron microscope specimens 50μm). Harvested 3 sets, one for 5-HT, a set of 5-HT2AR, set for control experiments. Floating immuno-histochemical staining method(ABC) was used to demonstrate the expressions of 5-HT and 5-HT2AR in ATN of rats, the pre-embedding immunohistochemical staining was used to demonstrate 5-HT positive axon terminal. Image analysis system measuring 5-HT immunohisto-chemical positive reaction of the average optical density (A),5-HT2AR immunohistochemical positive neurons in the gray value, all data applications SPSS 11.5 software paired T test.Results:15-HT immunohistochemistry showed that:Light microscope, there were a large number of 5-HT positive nerve fiber terminals distributed throughout the ATN. under the high microscope, fiber terminals running distances longer, beaded, stained in brown. In the anterior dorsal nucleus (AD), distribution of positive neurons and axon terminals were intensive, staining intensity were heavier compared with the anterior ventral thalamic nucleus(AV). There was a significant difference between them (p<0.05). No the 5-HT-like immunoreactivities were detected in the ATN of rats in control group.Electron microscope,showing 5-HT immunoreactive nerve axon terminals, terminal diameter (0.89±0.41)μm, (n= 131). Terminals were round or oval, containing round synaptic vesicles and mitochondria. And them formed asymmetric synaptic contacts with dendrites by axo-dendritic synapses or axis-body synapses.25-HT2AR immunohistochemistry showed that:5-HT2AR positive neurons appeared in ATN, to compared with AV, the positive neurons staining in the AD was more intensive and cell body was larger,which was significantly differ from that in the AV(p<0.05). The 5-HT2AR-like immunoreactivities were found chiefly on the membrane, and were not detected in the cytoplasm and nucleus. No the 5-HT2AR-like immuno-reactivities were detected in the ATN of rats in control group.Conclusions:1.A lot of 5-HT fiber terminals were richly distributed in the anterior thalamic nuclei, with a difference between AD and AV.2. 5-HT2AR were distributed in the anterior thalamic nuclei, with a difference between AD and AV.