EFFECTS OF CDP-CHOLINE ON ACETYLCHOLINE-INDUCED RELAXATION OF THE PERFUSED CAROTID VASCULAR BEDS OF THE RAT

1. The effects of an infusion of cytidine-5'-diphosphocholine (CDP-cho line) on the relaxation induced by exogenous acetylcholine (ACh) was s tudied in the isolated and perfuded external (ECB) and internal (ICB) carotid vascular beds of the rat. Changes in perfusion pressure were r ecorded during a dose-response curve to ACh and after a 30 min perfusi on with CDP-choline (1 mg/min). 2. ACh induced a dose-dependent relaxa tion in both vascular beds, indicating the presence of muscarinic rece ptors. The affinity of the receptors for ACh in the ICB was significan tly lower than in the ECB (ED(50): 120 +/- 21.4 ng and 69 +/- 10.3 ng, respectively). 3. In the ICB the infusion of CDP-choline for 30 min s ignificantly shifted the dose-response curve to ACh to the left, poten tiating the relaxation. This effect was not seen in the ECB. 4. The in fusion of hemicholinium (4 mu M) for 30 min together with CDP-choline completely prevented the potentiation of exogenous ACh-induced relaxat ion in the ICB. 5. The results of the present work suggest that CDP-ch oline is acting by increasing choline levels in the cholinergic nerve terminals of the ICB, increasing the synthesis and/or release of ACh.