RESISTANCE OF CENTRAL PHENYLETHANOLAMINE-N-METHYL TRANSFERASE CONTAINING NEURONS TO 6-HYDROXYDOPAMINE

  • 1 January 1976
    • journal article
    • research article
    • Vol. 54  (6) , 421-426
Abstract
The effects of the catecholamine neurotoxin 6-hydroxydopamine [6-OH-DA] on phenylethanolamine-N-methyl transferase (PNMT) in rat brain was investigated by biochemical and immunohistochemical analysis. 6-OH-DA was administered either intracisternally to adult rats or systematically to newborn rats, treatments known to affect markedly central noradrenaline neurons. None of these treatments had any significant effect on the PNMT activity in the hypothalamus, pons-medulla and the spinal cord, as measured in vitro using a radiometric assay. The neonatal 6-OH-DA treatment, which produced an almost complete noradrenaline denervation in the spinal cord, had no notable effect on the specific PNMT immunofluorescence localized in nerve terminals in the spinal cord. Transection of the spinal cord led to an almost complete disappearance of the PNMT activity and the specific immunofluorescence below the transection, pointing to the existence of a descending PNMT containing pathway in the spinal cord. The PNMT neurons were resistant to the neurotoxic action of 6-OH-DA, possibly due to lack of catecholamine uptake mechanism or due to these neurons having an uptake mechanism with a low affinity for 6-OH-Da. The noradrenaline and PNMT containing neurons apparently constitute separate neuron systems.

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