What exactly does "Inhibiting brain DA (dopamine) turnover" mean?

Treatment with aminooxyacetic acid (AOAA, 50 mg/kg i.p.) did not significantly change the concentrations of dopamine and noradrenaline in the rat brain. It markedly and similarly decelerated the disappearance of dopamine in the corpus striatum and the limbic system after treatment with dl-α-methytyrosine methylester (α-MT, 250 mg/kg i.p., 4 h) and accelerated the disappearance of noradrenaline. It also blocked the acceleration of the α-MT-induced dopamine, but not noradrenaline, disappearance caused by haloperidol. Administration of gamma-hydroxybutyric acid (GHBA, 1.5+1.0 g/kg i.p.) resulted in a larger retardation of the α-MT-induced dopamine disappearance which was about the same in the corpus striatum and the limbic system. Treatment with GHBA also increased the endogenous dopamine and this effect was significantly larger in the corpus striatum than in the limbic system like after an axotomy. The effect of AOAA may be due to accumulation of GABA inhibiting the cell bodies of the dopaminergic neurones.

Dopamine Turnover

Giving the context would be useful.

Under the assumption that you are referring to the mechanism of action of an anti-Parkinson's drug you are correct in saying less dopamine is broken down into metabolites.

Yes to the second question sort of... There will be more dopamine in the parts of the body where dopamine is released ie at the post synaptic membranes of neurons.

For the best answers, search on this site https://shorturl.im/awNiq

OK, dopamine is stored within the cells in your brain, and when its being used, it is released from these stores. Then later is is reabsorbed back into the cells. This drug will increase the levels of 'free' or 'extracellular' dopamine outside of your cells. It does this by stopping it being reabsorbed back into the stores. So it increases the amount of dopamine in use. Hope this explains it properly. And sorry if it sounds patronising, I explain things to myself like this.