Histaminergic axons in the neostriatum and cerebral cortex of the rat: a correlated light and electron microscopic immunocytochemical study using histidine decarboxylase as a marker.

Histaminergic nerve fibers and their axonal varicosities in the neostriatum and cerebral cortex were light and electronmicroscopically examined by means of peroxidase-antiperoxidase immunocytochemistry with histidine decarboxylase (HDC) as a marker. A majority of HDC-like immunoreactive axonal varicosities observed in serial thin sections for electron microscopy exhibited no synaptic contacts in either the neostriatum or cerebral cortex. The remaining small proportion of immunoreactive axonal varicosities formed synaptic contacts with non-immunoreactive dendritic shafts and spines.