Immunohistochemical localization of hyaluronic acid in rat and human brain.

The immunohistochemical localization of hyaluronic acid (HA) was studied in rat and human brain using the monoclonal antibody NDOG1, which specifically recognizes HA. In both rat and human brain, HA-like immunoreactivity formed characteristic coats around neurons in highly selective areas. The staining was abolished by pretreatment of sections with testicular and Streptomyces hyaluronidases, indicating that the staining was specific for HA. In rat brain, positive neurons were located in the cerebral cortex, subiculum, amygdala, thalamic reticular nucleus, nuclei of the inferior colliculus, nuclei of the trapezoid body, and vestibular nuclei. They were also scattered in the hypothalamus, substantia nigra pars reticularis, red nucleus, parabrachial nuclei, brainstem reticular nuclear group, ventral cochlear nucleus, nuclei of lateral lemniscus, and deep cerebellar nuclei. Double immunohistochemical studies showed that many neurons staining for HA were positive for parvalbumin, with minor exceptions in the amygdala and piriform cortex, where some HA-positive neurons were also positive for calbindin-D28k. In the areas studied in human brain, the distribution of HA-positive neurons was virtually identical to that in rat brain. HA-positive neurons were not significantly altered in Alzheimer disease (AD) brain, suggesting that these neurons are resistant to the pathological process of AD.