VIP-like immunoreactivity within neurons and perivascular neuronal processes of the human cerebral cortex

Using indirect immunocytochemical techniques, neurons with VIP (Vasoactive Intestinal Polypeptide)-like immunoreactivity (ir) have been demonstrated in the human cerebral cortex of the parietal lobe. In all the cortical layers containing positive neurons, perivascular immunoreactive neuronal processes have been detected: in arterioles, they are located in the adventitial and smooth muscle layers; in capillaries, they establish tight anatomical relations with the endothelium-pericyte layer and the perivascular glial sheath. Bodies of positive neurons have also been seen adhering to capillary walls. The detection of perivascular VIP-like ir provides morphological evidence of the role played by this polypeptide in the regulation of the cerebral blood flow. Moreover, the relationships between immunoreactive neuronal processes and perivascular glia might corroborate the suggestion that VIP is involved in the functioning of the blood-brain barrier.