Changes in steady-state levels of XXXX hydroxylase protein in adult @entity35 brain after neonatal @entity2955 lesion.

@entity935 @entity2340 @entity750 @entity35 @entity669 @entity2955
A recently developed technique of immunoautoradiography on nitrocellulose transfers of serial frozen sections was used to determine @entity2340 hydroxylase concentration in selected areas of the adult @entity35 brain following neonatal @entity2955 destruction of nigrostriatal @entity935 neurons. Particular attention was paid to the neostriatum, known to be @entity750 -hyperinnervated under these conditions, and to the nucleus raphe dorsalis, containing the cell bodies of origin for these nerve terminals. The hippocampus was also investigated as a territory of structurally intact @entity750 innervation arising primarily from the nucleus raphe medianus. @entity2340 hydroxylase protein was measured at successive transverse levels across the entire caudorostral extent of all these regions. Similar measurements of @entity669 hydroxylase protein across the substantia nigra and the neostriatum verified the disappearance of the nigrostriatal @entity935 neurons. The average @entity2340 hydroxylase tissue concentration in the dorsal third of the @entity750 -hyperinnervated neostriatum was up by 36% above control, i.e. significantly less than the number of its @entity750 axon terminals or varicosities. This was therefore indicative of a lowering of the @entity2340 hydroxylase protein content per @entity750 ending. Interestingly, a tight correlation between the respective level-by-level concentrations of @entity2340 hydroxylase and @entity669 hydroxylase protein in the control neostriatum allowed the prediction the @entity2340 hydroxylase concentration after @entity935 denervation with a @entity750 hyperinnervation. @entity2340 hydroxylase concentration was also significantly reduced in both the nucleus raphe dorsalis and nucleus raphe medianus, notably at those raphe dorsalis levels known to give rise to the @entity750 hyperinnervation of neostriatum. It is hypothesized that the lower steady-state level of @entity2340 hydroxylase inside the terminals and cell bodies of hyperinnervating @entity750 neurons was the result of a feedback inhibition of the synthesis of the enzyme by its end-product, presumably because of the increased amount of @entity750 in these terminals.
