Corticothalamic axons contact blood vessels as well as nerve cells in the thalamus

Corticothalamic axons in cats and rats were studied after labelling by intr acortical injections of axonally transported markers. Individual axons were traced to their terminal branches. Many preterminal segments had a tightly spiral or winding course which was often closely adjacent to a thalamic bl ood vessel. Electron micrographs of such axons showed them lying immediatel y adjacent to the vascular basement membrane, without the astrocytic cytopl asm that generally separates neural processes from the basement membrane of vessels. The functional nature of this neurovascular relationship remains to be explored.