Differences Between Cerebrovascular and Anti-Ischemic Effects of Dopamine, Docosahexaenoyldopamine, and GABA–Docosahexaenoyldopamine Conjugate

The cerebrovascular and anti-ischemic effects of dopamine and synthetic docosahexaenoyldopamine (DHA-DA) and the GABA–DHA-DA conjugate (OXL1220) were compared and found to differ. Dopamine and DHA-DA increased blood flow in intact and ischemic brain that was associated with pronounced hypertensive reactions. The latter inhibited dopamine transporter with IC 50 = 29 μM but was practically inactive as a ligand for dopamine receptors. OXL1220 produced a selective vasodilating effect on blood flow in brain subjected to transient global ischemia. Only OXL1220 competed in vitro for specific binding sites of [ 3 H]-gabazine in rat-brain GABA A -receptors. Therefore, conjugation of a neuromediator (GABA) to the DHA-DA changed the dopaminergic activity of the compound to GABA-ergic with respect to vascular tone in ischemic brain.