Dissociation between hypothalamic catecholamine levels and epinephrine-forming enzyme activity after midbrain...

We found decreased catecholamine (norepinephrine and epinephrine) levels in selective hypothalamic nuclei of the rat after complete midbrain hemitransections. In contrast, the activity of the epinephrine-forming enzyme (phenylethanolamine-N-methyltransferase, PNMT, EC 2.1.1.28) was unchanged in the hypothalamus after the lesions. Our results demonstrate a dissociation between hypothalamic catecholamine levels and PNMT activity, and suggest that hypothalamic PNMT may not be localized in catecholaminergic axons originating in the brainstem.