Density of the dopamine innervation in rat cerebral cortex after neonatal 6-hydroxydopamine or adult stage DSP-4 noradrenaline denervations: a quantitative radioautographic study.

An in vitro radioautographic approach was used to count dopamine axon terminals (varicosities) of the mediofrontal and the supragenual cingulate cortex in 30-40-day-old rats treated with 6-hydroxydopamine at birth or with N(2-chloro-ethyl)N-ethyl-2-bromobenzylamine hydrochloride (DSP-4) 7-10 days earlier. Compared to controls, there were no increases in the density of dopamine innervation in either region of the noradrenaline-denervated cortex after either treatment. The results, therefore, did not support the hypothesis of a sprouting of dopamine terminals reported to account for augmented cortical dopamine levels under these conditions. In line with earlier observations, such biochemical changes might rather be indicative of altered dopamine steady-state levels.