In Vivo and in Vitro Evidence for a Common Carrier Mediated Transport of Choline and Basic Drugs through the Blood-Brain Barrier

The blood-brain barrier (BBB) transport system for choline and basic drugs was characterized by the in vivo carotid artery injection technique (Oldendorf, Brain Res., 24, 372–376, 1970) and in vitro uptake into isolated bovine brain capillaries (Pardridge et al., J. Neurochem., 44, 1178–1184, 1985). Basic drugs such as eperisone, thiamine and scopolamine significantly inhibited choline uptake by the BBB with the half inhibitory concentration, IC50 value of 1.45, 2.06, and 0.47 mM, respectively. On the contrary, the uptake of choline was not inhibited by amino acids (L-phenylalanine and L-arginine) and acidic drugs (nicotinic acid, salicylic acid and valproic acid). Choline was taken up by the isolated brain capillaries in concentration and temperature dependent manners. The uptake of choline by the isolated bovine brain capillaries was significantly inhibited by eperisone, scopolamine and thiamine in consistent with the in vivo results. Furthermore, eperisone inhibited competitively the uptake of choline with the inhibition constant, K_i value of 455 μM. According to these results it was suggested that in the BBB choline and basic drugs would share a common carrier-mediated transport system.