Experimental Study Of Co-localization Of TH And HAP1 In Sympathetic Ganglia And Influence Of Chemical Sympathectomy On Expression Of HAP1 In Visceral Motor Ganglia In Rat

Huntingtin-associated protein 1 (HAP1) is a novel cytoplasmic protein, it was paid much attention because of its association with huntingtin protein, a Huntington's disease gene product. The celluar and subcelullar location of HAP1 in the central nervous system has been identified. HAP1 is extensively distributed in the rat/mouse brain, but this distribution has regional differences. Distribution of HAP1 in central nervous system has been reported in many literatures, and the hypothalamus exhibits the most intensely staining of HAP1 immunoreactivity. In peripheral nervous system, Min Liao et al. reported that HAP1 distributed in spinal ganglia and trigeminal ganglia. In visceral nervous system HAP1 was only found in the embryonic intestinal intramural ganglia and the abdominal sympathetic ganglia of mouse. We also discovered the extensive distribution of HAP1-IR positive neurons in the visceral motor ganglia of the adult rat by immunohistochemical method.Tyrosine hydroxylase (TH) is the rate-limiting enzyme of catecholamine synthesis with extensive distribution in sympathetic ganglia and sympathetic nerve fibers, and there are also reported that TH-IR positive productions distribute in some parasympathetic ganglia. In our laboratory we have discovered the extensive distribution of HAP1-IR positive products in the visceral motor ganglia and the co-localization of HAP1 and TH in the pelvic ganglia and intrinsic cardiac ganglia. These results provide morphological evidence for studying the mutual effects of HAP1 and TH in the parasympathetic ganglia. Hypothalamus is a critical area modulating the movements of viscera. The high expression of HAP1 in hypothalamus and extensive distribution in visceral motor ganglia suggested that HAP1 was probably associated with movement of viscera. But there is not report about the function of HAP1 in viscera. It is deserved to further study if HAP1 and TH have some interactions in the same neuron.In the first section of this experiment, we selected continuous slices of cervical and thoracic sympathetic trunk ganglia to study the co-localization of HAP1 and TH in the neurons of superior cervical ganglion (SCG), stellate ganglion (SG) and parts of the thoracic sympathetic trunk ganglia. The result of the immunohistochemistry staining displayed that the TH-IR products were brown, localized in cytoplasm and the nuclei were negative. The shapes of TH-IR positive neurons in the SCG, SG and thoracic sympathetic trunk ganglia are similar to that of the HAP1-IR positive neurons in the same ganglia. In the continuous slices of cervical and thoracic sympathetic trunk ganglia, the HAP1-IR positive neurons were also TH-IR positive, and only HAP1-IR positive or TH-IR positive neuron was not found.In the second section of this experiment, a model of de-sympathetic rat in this experiment was set up by intravenous administration of 100 mg/kg of 6-hydroxydopamine via the tail vein. Then the quantitative analysis for HAP1 in the visceral motor ganglia was performed by immunohistochemistry and image analysis. The result revealed that under light microscope considerable HAP1-IR positive neurons were seen in the intrinsic cardiac ganglia, lung ganglia, pelvic ganglia and sympathetic trunk ganglia. The HAP1-IR products were also brown, localized in cytoplasm and the nuclei were negative. The HAP1-IR positive neurons were round,elliptic or polygonal. The number of the neurons in the pelvic ganglia and sympathetic trunk ganglia was large, and there were many HAP-IR positive neurons in those ganglia. The intrinsic cardiac ganglia and lung ganglia distributed in the loose connective tissue of the posterior wall of atria and the hilum of lung respectively, and the number of HAP1-IR positive neurons was less. Compared with the control group, HAP1 expression in the sympathetic ganglia was increased in drug administrated group, but was decreased in the parasympathetic ganglion in rats of drug administrated group.The expression of HAP1 in both central and peripheral visceral motor nerve system suggested that HAP1 probably involved in some function adjustments of vegetative nervous system. HAP1 and TH not only co-localize in parasympathetic ganglia, but also co-localize in sympathetic ganglia. The significance of the co-localization was not clear. The changes of expression of HAP1 in visceral motor ganglia suggest that HAP1 may play an important role in regulation of the visceral movements and interact with the neurotransmitter.