Olfactory bulb removal: effects on brain norepinephrine.

Removal of one olfactory bulb causes marked changes in the norepinephrine contents of several brain regions. The brainstem catecholamine level is higher on the side of the lesion than on the control side, whereas telencephalic norepinephrine is lower ipsilateral to the lesion. The apparent decline in telencephalic norepinephrine is associated with a parallel decrease in the ability of this region to take up and retain (3)H-norepinephrine injected into the lateral cerebral ventricle. Within the ipsilateral olfactory tubercle, there is also a significant decrease in the activity of the enzyme phenylethanolamine-N-methyl transferase, which catalyzes the conversion of norepinephrine to epinephrine. The results of this study suggest that measurement of changes in the uptake of (3)H-norepinephrine injected into the cerebral ventricle can be used as a technique for mapping central adrenergic pathways.