Cortical and striatal in vivo uptake and metabolism of plasma choline in the rat: effects of haloperidol and apomorphine

Development of new levodopa treatment strategies in Parkinson's disease-from bedside to bench to bedside

This review will illustrate the process of moving from an idea through preclinical research and Galenic developments into clinical investigations and finally to approval by regulatory agencies within the European Union. The two new treatment strategies described, levodopa/carbidopa intestinal gel and levodopa/carbidopa microtablets, for advanced Parkinson's disease, have been developed in collaborative research within departments at Uppsala University. With this historical approach, reference priority is given to reports considered to be of special importance for this more than two decades long process 'from bedside to bench to bedside'.

Kinetics of [3H]choline and [3H]acetylcholine metabolism in several regions of rat brain following intracerebroventricular injection of [3H]choline. Effects of haloperidol

Intracerebroventricular (icv.) injection of [3H]choline in conscious rats produced a rapid, efficient labeling of brain choline and acetylcholine (ACh) stores without altering steady-state levels of endogenous ACh. The kinetics of [3H]choline and [3H]ACh metabolism were measured in seven brain regions for up to 10 min following icv. administration of [3H]choline. The initial rate of formation of [3H]ACh varied in different brain areas, being greatest in the striatum and least in the hypothalamus. In contrast, the rate of [3H]choline metabolism was similar in all regions of the brain. Pretreatment of rats with haloperidol resulted in an increase in the apparent synthesis rate of ACh only in the striatum and rostral hypothalamus, pointing to possible dopaminergic-cholinergic interaction in these regions.

In vivo turnover rate of acetylcholine in rat brain parts at elevated steady-state concentration of plasma choline

Cortical and striatal turnover rates of acetylcholine TR(ACh) were estimated by applying steady-state tracer kinetics in rats killed by microwave irradiation following a constant i.v. infusion of 3H-Ch. In control rats TR(ACh) was 3.6 nmol . g-1 . min-1 in the cortex and 23.8 nmol . g-1 . min-1 in the striatum. When steady-state plasma concentrations of Ch were increased from 17 to 140 mumol . 1-1 by a 15-min infusion of unlabelled Ch the corresponding TR(ACh) were 3.6 nmol . g-1 . min-1 and 21.4 nmol . g-1 . min-1, respectively. These results indicate that increased plasma levels of Ch are not accompanied by increased synthesis of brain ACh.