VARIATION OF MONOAMINES AND THEIR METABOLITE CONTENTS IN THE CEREBROSPINAL-FLUID OF CONSCIOUS RATS

To study the circadian rhythm of the monoamine and metabolite contents , cerebrospinal fluid was taken from the cisterna magna through a poly ethylene catheter tube every 4 hr in the conscious rat. Norepinephrine and 3-methoxy-4-hydroxy-phenylglycol were found to describe a rhythm with the maximal content occurring during the dark phase and the minim al content occurring during the light phase. Dopamine levels increased significantly during the light phase compared with the dark phase. Th ese results, given that cerebrospinal fluid can be taken chronically f rom conscious rats, indicate that our present method may be suitable f or estimating changes in brain monoamine and metabolite contents.