the origin of free 3-methoxy-4-hydroxyphenylethyleneglycol ( mhpg , a major metabolite of norepinephrine ) in rat cerebrospinal fluid ( csf ) was investigated using brain and spinal cord perfusions with artificial csf , electrical stimulation of the locus coeruleus ( lc ) and the technique of retrograde cell labelling with horseradish peroxidase ( hrp ) .
C0006104
brain
C0023951
locus coeruleus