Figure 4.

Molecular expression and vasomotor effects of microvascular receptors. Gel electrophoresis of PCR products for VIP (A), CCK (B), and SOM (C) receptor subtypes expressed in cultures of EC, SMC, and AST. Only products expressed in 50% or more of the cell cultures are illustrated. EC expressed all subtypes of VIP and CCK receptors and only SSTR1 and SSTR2. SMC were found to express all VIP receptor subtypes, no CCK receptors, and SSTR2 and SSTR4 receptors. In contrast, AST showed expression of PAC1, VPAC1, CCK-A, and CCK-B receptors and SSTR2 receptor subtypes. Samples without reverse transcriptase (-) were included to control for possible contamination. Vascular responses (mean ± SEM) were evoked in cortical slices by bath application of different substances known to colocalize in different subsets of GABA interneurons. After preconstriction with U46619, VIP induced a dilatation in 6 of 10 microvessels (A, right panel), whereas CCK failed to elicit any vasomotor response (B, right panel; n = 13). At baseline, most microvessels tested (9 of 10) were unresponsive to bath application of SOM (C, second panel) except for one, which constricted in phase with the peptide application (open circles). A majority (6 of 7) of vessels reversibly constricted after NPY application, whereas the NO donor DEA NONOate strongly and reversibly dilated microvessels (n = 6 of 14; C, third and forth panels, respectively).