Morphmetric Observation Of Autorhythmic Cell In Left Ventricular Outflow Tract In Guinea-Pig

Ventricular outflow tract, including pulmonary conus and aorticvestibule, used to be considered an output channel of the blood. So therehas been a lack of detailed studies on its structural characteristics andphysiological function have always In recent years, spontaneous slowaction potential could be recorded in the specific part of aortic vestibulein guinea-pig, rabbit and rat, which suggested that there were some cells inleft ventricular outflow tract to produce spontaneous slow action potential,and that might play an unknown role in heart activity. So little informationwas found in the traditional data and it had not caught enough attention.However, the nature of potential and ion current feature have been muchstudied recently, while morphmetric observation has not been furtherstudied up to now. The aim of the present experiments is to investigate tothe structural features of the organization and nerve distribution ofventricular outflow tract .Spontaneous slow action potential was recorded by using conventionalintracellular microelectrode technique and characteristics of spontaneousslow action potential were analyzed. We determined the distribution regionof self-regulatory cells by the above way, then the regions were made toparaffin block and were observed through light microscope by the way HE,Masson staining and silver staining and an electron microscope.Morphological structure of the specimen used. It was important to observethe structure of cells, collagen fibers and reticular fibers in the region tofurther determine the location of self-cells and ultrastructure of cells. Theeffect autonomic neurotransmitter observed about different concentrationson cells. We compared the neurotransmitter effect with the distribution of NPY nerve fibers by immunohistochemistry staining to observe the regionwhether to accept the regulation of autonomic nerve fibers.The results documented that spontaneous slow potential in most leftventricular outflow tract of guinea-pig was recorded, and moreover, lunarcells clump was observed in the borderline between area of arteriae rootand ventricular muscle by light microscope and electron microscope. Cellsgathered singly or in groups with plenty of collagen fibrils around cells.Cell morphosis is similar to the P-cell-like cells and it may be the part ofself-regulatory cells. These cell masses were surrounded by plenty ofcollagen fibers and reticular fibers that could play an important insulationand protection role for cell mass in groups of self-regulation on cellelectrical activity.Perfusate with the sympathetic neurotransmitters (NE, E) is able tosignificantly increase the values in the indices RPF, APA, VDD, Vmax,MDP, while the changes of index APD50 and APD90 were not obvious.However, Perfusated with the normal wash, the values of theabove-mentioned indices gradually restored. Perfusate With theparasympathetic neurotransmitter (ACh), could absolutely decrease thevalues of the indices RPF, APA, VDD, Vmax , MDP ,APD50 and APD90,but after switching to the normal wash, these values of indices recovered indifferent degrees. These results indicated that autonomic nerveneurotransmitter plays a significant role in the electrical activity of cells. Inthe surrounding connective tissue, we could see a large number ofNPY-positive nerve fibers by immunohistochemistry staining, and theshapes of which is linear or fascicular around cell mass, occasionallywithin cells. The neurotransmitter of NPY and NE existed in the samenerve fibers endings, so it showed that the cells that produced electricalactivity could also be regulated by sympathetic nerve fibers.In summary, there were specific cell clusters that generated slowaction potentials in the left ventricular outflow tract. NPY-positive nerve fibers by immunohistochemistry staining existed in the part, whichindicated these cell clusters in the left ventricular outflow tract mightaccept the regulation of sympathetic nerve.