DEGENERATIVE AND NONDEGENERATIVE EFFECTS OF 6-HYDROXYDOPAMINE ON ADRENERGIC NERVES

¹ Department of Histology, Karolinska Institutet, Stockholm, Sweden

The short-term effects of 6-hydroxydopamine (6-OHDA) on the norepinephrine content, ³H-norepinephrine and ³H-metaraminol uptake and nerve density of adrenergic nerve terminals have been investigated in mouse heart and iris. The results obtained show that all the parameters investigated were quantitatively reduced to approximately the same degree after all doses and time intervals studied. 6-OHDA administered in vivo thus seems to act on the adrenergic nerves very much in an "all or none" fashion with a complete destruction of norepinephrine uptake-storage mechanisms in a proportion of nerves depending on the dose used, while the remaining nerves are left with more or less intact transmitter mechanisms. Displacement plays a minor role in the depleting action of 6-OHDA. The results obtained furthermore support the view that a destruction of the membrane uptake mechanism of the adrenergic neuron is a very early sign in the degeneration process caused by 6-OHDA.

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