Figure 7.
Schematic representation of the suggested role of cortical interneurons in neurovascular coupling and as possible relay neurons for vasoactive basal forebrain (BF) ACh and brainstem 5-HT systems. Their direct vasomotor effects are thought to be mediated by m5 muscarinic ACh receptor (dilatation) or 5-HT1B receptor (constriction). However, the ability of these systems to target cortical GABA interneurons projecting to local microvessels that are endowed with subtype-specific receptors for vasoactive neuropeptides (VIP, NPY, or SOM) colocalized with GABA strongly support a role of cortical interneurons in modulating microvascular tone. A role for perivascular astrocytes cannot be excluded because they are neuropeptide receptive and are known to release vasodilatory mediators. Note that there is no receptor for CCK on smooth muscle cells and that this peptide failed to induce any vasomotor response. Also, cortical interneurons could serve as local relays in neurovascular coupling for other vasoactive afferent pathways (e.g., glutamate) (see Discussion).