Nicotinic cholinergic receptors associated with mammalian cerebral vessels

Current evidence suggests that the cerebral vasculature may be modulated by cholinergic nerves. We used ligand binding methods to examine the presence of nicotinic cholinergic receptors in brain vasculature. We found carbachol-displaceable [3H]acetylcholine (ACh) and [3H]nicotine (NIC) binding sites in preparations of intraparenchymal cerebral microvessels (CMV) and larger pial vessels from human and pig brains. Specific binding sites for [3H]ACh and [3H]NIC in cerebral microvessels were saturable and comparable in density to those in cerebral cortex. The Kds for the two ligands ranged 3-18 nM whereas the Bmaxs were 25-45 fmol/mg protein. In contrast, the binding of [3H]pirenzipine or [3H]quinuclidinyl benzilate, index for muscarinic receptors, was low (9-15% of cortex) in microvessels compared to the cerebral cortex. Our observations suggest the association of cholinergic nicotinic receptors with cerebral microvessels, which may be involved in the modulation of the cerebral circulation by cholinergic neurons.