An investigation into the possible relationship of adenosine triphosphate to sensory synaptic transmitter substances

An attempt has been made to determine the relationship, if any, between adenosine triphosphate and the transmitter substance responsible for antidromic vasodilatation. Extracts of various areas of the central nervous system have been made by dialyzing boiled, ground brain tissue against distilled water. These extracts were analyzed for; labile phosphate content by the method of Berenblum and Chain (66), adenosine triphosphate content by paper chromatography and by the luciferin-luciferase enzyme method of Strehler and Totter (69). The content of vasodilator activity of extracts from the same areas was determined by the method of Holton (35). The extracts to be tested were injected into the facial artery of a rabbit and allowed to flow into the auricular artery and through the ear. The changes produced in the ear were detected by means of a photoelectric cell which measured differences in the amount of light passing through the ear. Vasodilatation appeared as a decrease in the amount of light transmitted through the ear and vasoconstriction as an increase. It was thought that if there was a relationship between adenozine triphosphate and the transmitter material the areas containing the most ATP should also contain the most vasodilator activity. A comparison of the location and concentration of the two substances revealed no such correlation. The two most important questions to be answered were: 1. is ATP the substance responsible for antidromic vasodilatation? and 2. if so, is it also a sensory synaptic transmitter substance? It was concluded that ATP was unlikely to be the substance responsible for antidromic vasodilatation. If one accepts Dale's hypothesis (48) that a neurone may employ the same transmitter substance at all branches of the axon, then it would also seem to rule out ATP as a sensory synaptic transmitter agent.Medicine, Faculty ofCellular and Physiological Sciences, Department ofGraduat