Submitted on December 3, 2004
Accepted on February 4, 2005
Modulation of cerebral microvascular permeability by endothelial nicotinic acetylcholine receptors
Brian T Hawkins1*, Richard D Egleton2, and Thomas P Davis3
1 Program in Neuroscience, The University of Arizona, Tucson, AZ, USA
2 Department of Medical Pharmacology, The University of Arizona College of Medicine, Tucson, AZ, USA
3 Program in Neuroscience, The University of Arizona, Tucson, AZ, USA; Department of Medical Pharmacology, The University of Arizona College of Medicine, Tucson, AZ, USA
* To whom correspondence should be addressed. E-mail: bhawkins{at}u.arizona.edu.
Nicotine increases the permeability of the blood-brain barrier in vivo. This implies a possible role for nicotinic acetylcholine receptors in the regulation of cerebral microvascular permeability. Expression of nicotinic acetylcholine receptor subunits in cerebral microvessels was investigated using immunofluorescence microscopy. Positive immunoreactivity was found for receptor subunits 
3, 5, 7, and 
2, but not subunits 4, 3, or 4. Blood-brain barrier permeability was assessed via in situ brain perfusion with [14C]-sucrose. Nicotine increased the rate of sucrose entry into the brain from 0.3 ± 0.1 µl g-1 min-1 to 1.1 ± 0.2 µl g-1 min-1, as previously described. This nicotine-induced increase in blood-brain barrier permeability was significantly attenuated by both the blood-brain barrier permeable nicotinic antagonist mecamylamine and the blood-brain barrier impermeable nicotinic antagonist hexamethonium to 0.5 ± 0.2 µl g-1 min-1 and 0.3 ± 0.2 µl g-1 min-1, respectively. These data suggest that nicotinic acetylcholine receptors expressed on the cerebral microvascular endothelium mediate nicotine-induced changes in blood-brain barrier permeability.
