NICOTINIC CHOLINERGIC RECEPTORS ASSOCIATED WITH MAMMALIAN CEREBRAL VESSELS

Current evidence suggests that the cerebral vasculature may be modulat ed by cholinergic nerves. We used ligand binding methods to examine th e presence of nicotinic cholinergic receptors in brain vasculature. We found carbachol-displaceable [H-3]acetylcholine (ACh) and [H-3]nicoti ne (NIC) binding sites in preparations of intraparenchymal cerebral mi crovessels (CMV) and larger pial vessels from human and pig brains. Sp ecific binding sites for [H-3]ACh and [H-3]NIC in cerebral microvessel s were saturable and comparable in density to those in cerebral cortex . The K(d)s for the two ligands ranged 3-18 nM whereas the B(max)s wer e 25-45 fmol/mg protein. In contrast, the binding of [H-3]pirenzipine or [H-3]quinuclidinyl benzilate, index for muscarinic receptors, was l ow (9-15% of cortex) in microvessels compared to the cerebral cortex. Our observations suggest the association of cholinergic nicotinic rece ptors with cerebral microvessels, which may be involved in the modulat ion of the cerebral circulation by cholinergic neurons.