Effects of Intraventricular Injections of 6-hydroxydopamine (6-0HDA) on adrenocortical cell proliferation in rats have been Investigated by means of the colchicine metaphase-arrest technique. in the group of animals receiving 6-OHDA alone, an Increase of mean mitotic activity rate (MMAR) was observed at 96 h and 144 h after Injection. This rise of MMAR was completely inhibited by pretreatment of animals with desmethylimipramine (DMI) - a blocker of norepinephrine uptake. It is concluded that enhancement of ACTH secretion Is responsible for the above mentioned Increase of mitottc activity after 6-OHDA administration. This phenomenon is related to abolition of the Inhibitory noradrenergic effect on ACTH secretion by 6-OHDA treatment. Additionally, the results suggest little or no involvement of dopaminergic neurons in early changes of ACTH secretion after Intraventricular 6-OHDA.
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