Adrenergic innervation of the mammalian choroid plexus

Choroid plexuses from the four cerebral ventricles of mice, rats, guinea‐pigs, rabbits, cats, cows, and monkeys were either sectioned after freeze‐drying or stretched on microscope slides for subsequent exposure to formaldehyde gas to demonstrate fluorescent adrenergic nerves. All plexuses received a substantial amount of noradrenaline‐containing axons which originated in the superior cervical sympathetic ganglia. The nerve terminals enclosed both arterial and venous vessels. Some of the terminals in the tufts of the choroid plexus ran between the base of the epithelial cells and the underlying vascular wall. Thus, there are structural possibilities for a sympathetic innervation of the plexus epithelium, the plexus blood vessels, or both.